Modular QoS Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.3.x

Packet Classification Overview

Table 1. Feature History Table
Feature Name	Release Information	Feature Description
Cisco NC57 Compatibility Mode: QoS Enablement on Layer 2 MPLS/BGP	Release 7.3.1	This feature is now supported on routers that have the Cisco NC57 line cards installed and operate in the compatibility mode. The following Layer 2 services are supported: Local switching [xconnect or bridging] Layer 2 VPN – Virtual Private Wire Service (VPWS) Apart from packet classification, this feature is available for the following QoS operations: Modular QoS Congestion Avoidance Configuring Modular QoS Congestion Management QoS on Link Bundles Configuring Hierarchical Modular QoS

Packet classification involves categorizing a packet within a specific group (or class) and assigning it a traffic descriptor to make it accessible for QoS handling on the network. The traffic descriptor contains information about the forwarding treatment (quality of service) that the packet should receive. Using packet classification, you can partition network traffic into multiple priority levels or classes of service. The source agrees to adhere to the contracted terms and the network promises a quality of service. Traffic policers and traffic shapers use the traffic descriptor of a packet to ensure adherence to the contract.

Traffic policers and traffic shapers rely on packet classification features, such as IP precedence, to select packets (or traffic flows) traversing a router or interface for different types of QoS service. After you classify packets, you can use other QoS features to assign the appropriate traffic handling policies including congestion management, bandwidth allocation, and delay bounds for each traffic class.

The Modular Quality of Service (QoS) CLI (MQC) defines the traffic flows that must be classified, where each traffic flow is called a class of service, or class. Later, a traffic policy is created and applied to a class. All traffic not identified by defined classes fall into the category of a default class.

You can classify packets at the ingress on L3 subinterfaces for (CoS, DEI) for IPv4, IPv6, and MPLS flows. IPv6 packets are forwarded by paths that are different from those for IPv4. To enable classification of IPv6 packets based on (CoS, DEI) on L3 subinterfaces, run the hw-module profile qos ipv6 short-l2qos-enable command and reboot the line card for the command to take effect.

Traffic Class Elements

The purpose of a traffic class is to classify traffic on your router. Use the class-map command to define a traffic class.

A traffic class contains three major elements:

A name
A series of match commands - to specify various criteria for classifying packets.
An instruction on how to evaluate these match commands (if more than one match command exists in the traffic class)

Packets are checked to determine whether they match the criteria that are specified in the match commands. If a packet matches the specified criteria, that packet is considered a member of the class and is forwarded according to the QoS specifications set in the traffic policy. Packets that fail to meet any of the matching criteria are classified as members of the default traffic class.

This table shows the details of match types that are supported on the router.


Match Type Supported	Min, Max	Max Entries	Support for Match NOT	Support for Ranges	Direction Supported on Interfaces
IPv4 DSCP IPv6 DSCP DSCP	(0,63)	64	Yes	Yes	Ingress
IPv4 Precedence IPv6 Precedence Precedence	(0,7)	8	Yes	No	Ingress
MPLS Experimental Topmost	(0,7)	8	Yes	No	Ingress
Access-group	Not applicable	8	No	Not applicable	Ingress
QoS-group	(1,7) (1,511) for peering profile	7	No	No	Egress Ingress for QoS Policy Propagation Using Border Gateway Protocol (QPPB) Ingress for peering profile
Traffic-class	(1,7)	7	No	No	Egress
Protocol	(0,255)	1	Yes	Not applicable	Ingress

Note

Egress queue statistics are displayed only for those classes which have a corresponding match criteria in the egress. Therefore, if you have a set traffic-class x configured in the ingress, you must have a corresponding match traffic-class x in the egress, in order to see the statistics in the egress side.

Note

A maximum value of up to 64 unique queues is supported. Each unique queue-limit consumes one rate profile in the Traffic manager. Out of 64 unique queues, few are reserved for default configs and the remaining are usable.

Depending on the interface speeds, default configurations consume some of the rate profiles. The remaining rate profiles can be exhausted in the following scenarios:

Different shape rates without configuring queue limits could exhaust the rate profiles as 10ms of guaranteed service rate converts to a different value in bytes based on the shape rate.
Configuring queue limits in units of time could exhaust the rate profiles. For example, 20 ms of 50 Mbps and 20 ms of 100 Mbps are two different values in bytes.

Tip

You can avoid exhausting rate profiles by configuring queue limits in absolute units (such as bytes, kilobytes, or megabytes) for class maps and sharing these limits with the policy maps.

Default Traffic Class

Unclassified traffic (traffic that does not meet the match criteria specified in the traffic classes) is treated as belonging to the default traffic class.

If the user does not configure a default class, packets are still treated as members of the default class. However, by default, the default class has no enabled features. Therefore, packets belonging to a default class with no configured features have no QoS functionality. These packets are then placed into a first in, first out (FIFO) queue and forwarded at a rate determined by the available underlying link bandwidth. This FIFO queue is managed by a congestion avoidance technique called tail drop.

For egress classification, match on traffic-class (1-7) is supported. Match traffic-class 0 cannot be configured. The class-default in the egress policy maps to traffic-class 0 .

This example shows how to configure a traffic policy for the default class:


configure
 policy-map ingress_policy1
 class class-default
  police rate percent 30
 !

Create a Traffic Class

To create a traffic class containing match criteria, use the class-map command to specify the traffic class name, and then use the match commands in class-map configuration mode, as needed.

Guidelines

Users can provide multiple values for a match type in a single line of configuration; that is, if the first value does not meet the match criteria, then the next value indicated in the match statement is considered for classification.
Use the not keyword with the match command to perform a match based on the values of a field that are not specified.
All match commands specified in this configuration task are considered optional, but you must configure at least one match criterion for a class.
If you specify match-any , one of the match criteria must be met for traffic entering the traffic class to be classified as part of the traffic class. This is the default. If you specify match-all , the traffic must match all the match criteria.
From Release 7.7.1 onwards, for the match access-group command, QoS classification based on the packet length field in the IPv4 and IPv6 headers is supported. Prior to this, support was not available for packet length and TTL (time to live) fields.
For the match access-group command, when an ACL list is used within a class-map, the deny action of the ACL is ignored and the traffic is classified based on the specified ACL match parameters.

An empty ACL (contains no rules, only remarks), when used within a class-map permits all traffic by default, and the implicit deny condition doesn’t work with an empty ACL. The corresponding class-map matches all traffic not yet matched by the preceding traffic classes.
The traffic-class and discard-class are supported only in egress direction, and these are the only match criteria supported in egress direction.
The egress default class implicitly matches qos-group 0 for marking policy and traffic-class 0 for queuing policy.
Multicast takes a system path that is different than unicast on router, and they meet later on the egress in a multicast-to-unicast ratio of 20:80 on a per interface basis. This ratio is maintained on the same priority level as that of the traffic.
Egress QoS for multicast traffic treats traffic classes 0-5 as low-priority and traffic classes 6-7 as high priority. Currently, this is not user-configurable.
Egress shaping does not take effect for multicast traffic in the high priority (HP) traffic classes. It only applies to unicast traffic.
If you set a traffic class at the ingress policy and do not have a matching class at egress for the corresponding traffic class value, then the traffic at ingress with this class will not be accounted for in the default class at the egress policy map.
Only traffic class 0 falls in the default class. A non-zero traffic class assigned on ingress but with no assigned egress queue, falls neither in the default class nor any other class.

Configuration Example

You have to accomplish the following to complete the traffic class configuration:

Creating a class map
Specifying the match criteria for classifying the packet as a member of that particular class

(For a list of supported match types, see Traffic Class Elements.)


Router# configure
Router(config)# class-map match-any qos-1
Router(config-cmap)# match qos-group 1
Router(config-cmap)# end-class-map
Router(config-cmap)# commit

Use this command to verify the class-map configuration:


Router#show class-map qos-1
1) ClassMap: qos-1    Type: qos
    Referenced by 2 Policymaps

Also see, Running Configuration.

Also see, Verification.

Associated Commands

Traffic Policy Elements

A traffic policy contains three elements:

Name
Traffic class
QoS policies

After choosing the traffic class that is used to classify traffic to the traffic policy, the user can enter the QoS features to be applied to the classified traffic.

The MQC does not necessarily require that the users associate only one traffic class to one traffic policy.

The order in which classes are configured in a policy map is important. The match rules of the classes are programmed into the TCAM in the order in which the classes are specified in a policy map. Therefore, if a packet can possibly match multiple classes, only the first matching class is returned and the corresponding policy is applied.

The router supports 32 classes per policy-map in the ingress direction and 8 classes per policy-map in the egress direction.

This table shows the supported class-actions on the router.


Supported Action Types	Direction supported on Interfaces
minimum-bandwidth	egress
bandwidth-remaining*	egress
mark	(See Packet Marking)
police	ingress
priority	egress (level 1 to level 7)
queue-limit	egress
shape	egress
wred	egress

*Bandwidth and Bandwidth remaining configurations are not supported simultaneously within the same policy-map in H-QoS mode.

WRED supports default and discard-class options; the only values to be passed to the discard-class being 0 and 1.

Create a Traffic Policy

The purpose of a traffic policy is to configure the QoS features that should be associated with the traffic that has been classified in a user-specified traffic class or classes.

To configure a traffic class, see Create a Traffic Class.

After you define a traffic policy with the policy-map command, you can attach it to one, or more interfaces to specify the traffic policy for those interfaces by using the service-policy command in interface configuration mode. With dual policy support, you can have two traffic policies, one marking and one queuing attached at the output. See, Attach a Traffic Policy to an Interface.

Configuration Example

You have to accomplish the following to complete the traffic policy configuration:

Creating a policy map that can be attached to one or more interfaces to specify a service policy
Associating the traffic class with the traffic policy
Specifying the class-action(s) (see Traffic Policy Elements)


Router# configure
Router(config)# policy-map  test-shape-1
Router(config-pmap)# class qos-1

/* Configure class-action ('shape' in this example). 
Repeat as required, to specify other class-actions */
Router(config-pmap-c)# shape average percent 40
Router(config-pmap-c)# exit

/* Repeat class configuration as required, to specify other classes */

Router(config-pmap)# end-policy-map
Router(config)# commit

See, Running Configuration.

See, Verification.

Associated Commands

Scaling of Unique Ingress Policy Maps

Table 2. Feature History Table
Feature Name	Release Information	Feature Description
Scaling of Unique Ingress Policy Maps	Release 7.3.1	With this feature, unique policy maps associated to the same template are shared in TCAM, thus enabling scaling of — or creating more number of — policy maps.

Traditionally, when unique policy maps were associated to the same template — that is, having the same match criteria and actions in the same order — each map was assigned a different TCAM entry. This resulted in inefficient TCAM entry management and also restricted the number of policy maps that could be created.

With this functionality, unique policy maps associated to the same template are shared in TCAM, thus enabling scaling of—in other words, creating more number of—policy maps. The other way to understand this functionality is that two policy maps with the same combination of criteria and actions use one template. This way, up to 250 templates are supported for association to policy map combinations.

As an example, consider the following policy maps (policy-map ncs_input1 and policy-map ncs_input2) having the same class maps (class COS7_DEI0 and class COS7_DEI1):

class-map match-all COS7_DEI0
 match cos 0
 end-class-map
class-map match-all COS7_DEI1
 match cos 1
 end-class-map

policy-map ncs_input1
 class COS7_DEI0
  set trafiic class 1
  police rate 10 mbps
!
 class COS7_DEI1
  set traffic class 2
  policer rate 20 mbps
!

policy-map ncs_input2
 class COS7_DEI0
  set traffic class 1
  police rate 30 mbps
!
 class COS7_DEI1
  set traffic class 2
  policer rate 40 mbps
!

Earlier, when the policy maps were attached to interface, they used different TCAM entries, although the match criteria and actions were the same, except for the policer action.

With this functionality, both policy maps share the TCAM entry instead of selecting different entries, thus freeing up TCAM entries for more policy maps.

Limitations and Restrictions

Policy Maps share TCAM entries only for the same match criteria and actions or template. However, the policer action can be different for the same template.

For all unique policy maps the maximum number of templates supported is 250.

Attach a Traffic Policy to an Interface

After the traffic class and the traffic policy are created, you must attach the traffic policy to interface, and specify the direction in which the policy should be applied.

Note

When a policy-map is applied to an interface, the transmission rate counter of each class is not accurate. This is because the transmission rate counter is calculated based on the exponential decay filter.

Configuration Example

You have to accomplish the following to attach a traffic policy to an interface:

Creating a traffic class and the associated rules that match packets to the class (see )
Creating a traffic policy that can be attached to one or more interfaces to specify a service policy (see Create a Traffic Policy )
Associating the traffic class with the traffic policy
Attaching the traffic policy to an interface, in the ingress or egress direction


Router# configure
Router(config)# interface HundredGigE 0/6/0/18
Router(config-int)# service-policy output test-shape-1
Router(config-int)# commit

Running Configuration


/* Class-map configuration */

class-map match-any traffic-class-1
 match traffic-class 1
 end-class-map
!
- - -
- - -

/* Traffic policy configuration */
policy-map test-shape-1
 class traffic-class-1
  shape average percent 40
 !
 class class-default
 !
 end-policy-map
!
- - -
- - -

/* Attaching traffic policy to an interface in egress direction */ 
interface HundredGigE0/6/0/18
 service-policy output test-shape-1
 !

Verification


Router# show qos interface hundredGigE 0/6/0/18 output 

NOTE:- Configured values are displayed within parentheses Interface HundredGigE0/6/0/18 ifh 0x30001f8  -- output policy
NPU Id:                        3
Total number of classes:       2
Interface Bandwidth:           100000000 kbps
VOQ Base:                      11112
VOQ Stats Handle:              0x88430698
Accounting Type:               Layer1 (Include Layer 1 encapsulation and above)
------------------------------------------------------------------------------
Level1 Class                             =   qos-1
Egressq Queue ID                         =   11113 (LP queue)
Queue Max. BW.                           =   40329846 kbps (40 %)
Queue Min. BW.                           =   0 kbps (default)
Inverse Weight / Weight                  =   1 / (BWR not configured)
Guaranteed service rate                  =   40000000 kbps
TailDrop Threshold                       =   50069504 bytes / 10 ms (default)
WRED not configured for this class

Level1 Class                             =   class-default
Egressq Queue ID                         =   11112 (Default LP queue)
Queue Max. BW.                           =   101803495 kbps (default)
Queue Min. BW.                           =   0 kbps (default)
Inverse Weight / Weight                  =   1 / (BWR not configured)
Guaranteed service rate                  =   50000000 kbps
TailDrop Threshold                       =   62652416 bytes / 10 ms (default)
WRED not configured for this class

Associated Commands

service-policy

Packet Marking

Note

L2 packet marking is not supported on NC57-24DD and NC57-18DD-SE line cards for Cisco IOS XR Release 7.0.2.

The packet marking feature provides users with a means to differentiate packets based on the designated markings. The router supports egress packet marking. match on discard-class on egress, if configured, can be used for a marking policy only.

The router also supports L2 ingress marking.

For ingress marking:

Ingress traffic— For the ingress pop operation, re-marking the customer VLAN tag (CoS, DEI) is not supported.

Egress traffic— The ingress ‘pop VLAN’ is translated to a ‘push VLAN’ for the egress traffic, and (CoS, DEI) marking is supported for newly pushed VLAN tags. If two VLAN tags are pushed to the packet header at the egress side, both inner and outer VLAN tags are marked. For example:

1. rewrite ingress tag pop 1 symmetric

2. rewrite ingress tag pop 2 symmetric

3. rewrite ingress tag translate 2-to-1 dot1q/dot1ad <> symmetric

In case of pop action, the outer VLAN tag (CoS, DEI) is retained on NC57 line cards.

Single tag— When symmetrical pop 1 action is performed, the outer tag (CoS, DEI) is retained as the original frame.

Double tag— When symmetrical pop 2 action is performed, the outer tag (CoS, DEI) is retained as the original frame and inner tag (CoS, DEI) is set to 0/0.

Packet Marking Guidelines and Limitations

While marking a packet, ensure you don’t set the IP DSCP (using the set dscp command) and the MPLS experimental imposition values (using the set mpls experimental imposition command) for the same class map. Else, neither the DSCP remarking nor the MPLS EXP values may take effect at the ingress. This will cause, per default QoS behavior, the IP precedence values to be copied to the EXP bits on the imposed packets. Such an action could lead to unintended packets marked as high-priority by your customer being forwarded as high-priority MPLS packets in the network.
The statistics and counters for the egress marking policy cannot be viewed on the router.
QoS EXP matching for egress doesn’t work for Layer 2 VPN and Layer 3 VPN traffic flowing from:
- Cisco NCS 5700 series line cards at ingress to Cisco NCS 5500 series line cards at the egress
and
- from Cisco NCS 5500 series line cards at ingress to Cisco NCS 5700 series line cards at egress.
For QOS EXP-Egress marking applied on a Layer 3 interface on Cisco NCS550x and NCS55Ax routers, there is a limit of two unique policy maps per NPU. This limit is three unique policy maps per NPU for routers that have the Cisco NC57 line cards installed.

You can apply these policies to as many interfaces as your system resources allow. However, if you apply more than the permitted limit of unique policies, you may encounter unexpected failure.
For QOS egress marking (CoS, DEI) applied on a Layer 2 interface, there is a limit of 13 unique policy-maps per NPU. If you exceed this number, you may encounter unexpected failure.

Supported Packet Marking Operations

This table shows the supported packet marking operations.


Supported Mark Types	Range	Support for Unconditional Marking	Support for Conditional Marking
set dscp	0-63	ingress	No
set QoS-group	0-7	ingress	No
set traffic-class	0-7	ingress	No

Class-based Unconditional Packet Marking

The packet marking feature allows you to partition your network into multiple priority levels or classes of service, as follows:

Use QoS unconditional packet marking to set the IP precedence or IP DSCP values for packets entering the network. Routers within your network can then use the newly marked IP precedence values to determine how the traffic should be treated.

On ingress direction, after matching the traffic based on either the IP Precedence or DSCP value, you can set it to a particular discard-class. Weighted random early detection (WRED), a congestion avoidance technique, thereby uses discard-class values to determine the probability that a packet is dropped.

If however, you set a discard-class of 3, the packet is dropped at ingress itself.

Use QoS unconditional packet marking to assign MPLS packets to a QoS group. The router uses the QoS group to determine how to prioritize packets for transmission. To set the traffic class identifier on MPLS packets, use the set traffic-class command in policy map class configuration mode.

Note

Setting the traffic class identifier does not automatically prioritize the packets for transmission. You must first configure an egress policy that uses the traffic class.

Note

Unless otherwise indicated, the class-based unconditional packet marking for Layer 3 physical interfaces applies to bundle interfaces.

From IOS XR Release 7.2.1 onwards with NC57 line cards, propagation of PREC->COS marking happens by default on egress Layer 3 subinterfaces. This applies to single and double-tag L3 subinterfaces, and to NC57 line cards in Native mode.

QoS Re-marking of IP Packets in Egress Direction

The router support the marking of IP DSCP bits of all IP packets to zero, in the egress direction. This feature helps to re-mark the priority of IP packets, which is mostly used in scenarios like IP over Ethernet over MPLS over GRE. This functionality is achieved using the ingress policy-map with set dscp 0 option configured in class-default.

Configuration Example


Router# configure
Router(config)# policy-map ingress-set-dscp-zero-policy
Router(config-pmap)# class class-default 
Router(config-pmap-c)# set dscp 0
Router(config-pmap-c)# end-policy-map
Router(config-pmap)# commit

Running Configuration


policy-map ingress-set-dscp-zero-policy
class class-default
  set dscp 0
! 
end-policy-map
!

QoS Re-marking of Ethernet Packets in Egress Direction

The router supports Layer 2 marking of Ethernet packets in the egress direction.

QoS L2 Re-marking of Ethernet Packets in Egress Direction

The router supports Layer 2 marking of Ethernet packets in the egress direction.

To enable this feature, you must:

Configure the policy maps for queuing and marking at the egress interface.
Set traffic-class in the ingress and use match traffic-class in the egress for queuing.
Ensure that the set qos-group command is configured in ingress policy and the corresponding match qos-group command is configured in the egress marking policy. If there is no corresponding QoS group, you will experience traffic failure.

The ingress ‘push VLAN’ is translated to ‘pop VLAN’ for the egress traffic. In this case, (CoS, DEI) re-marking is not supported for the VLAN tag. For example:

1. rewrite ingress tag push dot1q/dot1ad <> symmetric

2. rewrite ingress tag push dot1q/dot1ad <> second-dot1q <> symmetric

3. rewrite ingress tag translate 1-to-2 dot1q/dot1ad <> second-dot1q <> symmetric

Running Configuration

policy-map egress-marking
class qos1
set cos 1
! 
class qos2
set cos 2
set dei 1
! 
class qos3
set cos 3
! 
class class-default
set cos 7
! 
end-policy-map
!

QoS L2 Re-Marking of Ethernet Packets on L3 Flows in Egress Direction

The router supports Layer 2 marking of Ethernet packets on Layer 3 flows in the egress direction.

To enable this feature, you must:

Configure the policy maps for marking at the egress interface.
Ensure that the set qos-group command is configured in ingress policy and the corresponding match qos-group command is configured in the egress marking policy. If there is no corresponding QoS group, you will experience traffic failure.

Restrictions

The following restrictions apply while configuring the Layer 2 marking of Ethernet packets on Layer 3 flows in the egress direction.

set discard-class is not supported in ingress policy with peering mode.
Egress marking statistics are not available.
Layer 2 (802.1p) Egress marking is supported on Layer 3 flows for these types of traffic: IP-to-IP, IP-to-MPLS, and MPLS-to-IP traffic.
Layer 2 marking of Ethernet packets on Layer 3 flows in the egress direction is supported only in the peering mode.

Running Configuration

Ingress Policy:

You must first set up the qos-group at ingress.

class-map match-any Class0
 match mpls experimental topmost 0
 match precedence routine
 match dscp 0-7
 end-class-map
class-map match-any Class1
 match mpls experimental topmost 1
 match precedence priority
 match dscp 8-15
 end-class-map
class-map match-any Class2
 match mpls experimental topmost 2
 match precedence immediate
 match dscp 16-23
 end-class-map
class-map match-any Class3
 match mpls experimental topmost 3
 match precedence flash
 match dscp 24-31
 end-class-map
class-map match-any Class4
 match mpls experimental topmost 4
 match precedence flash-override
 match dscp 32-39
 end-class-map
class-map match-any Class5
 match mpls experimental topmost 5
 match precedence critical
 match dscp 40-47
 end-class-map
class-map match-any Class6
 match mpls experimental topmost 6
 match precedence internet
 match dscp 48-55
 end-class-map
class-map match-any Class7
 match mpls experimental topmost 7
 match precedence network
 match dscp 56-63
 end-class-map
!

policy-map ncs_input
 class Class7
  set traffic-class 7
  set qos-group 7
!
 class Class6
  set traffic-class 6
  set qos-group 6
!
 class Class5
  set traffic-class 5
  set qos-group 5
!
 class Class4
  set traffic-class 4
  set qos-group 4
 !
 class Class3
  set traffic-class 4
  set qos-group 3
 !
 class Class2
  set traffic-class 2
  set qos-group 2
 !
 class Class1
  set traffic-class 2
  set qos-group 1
 !
 class Class0
  set traffic-class 0
  set qos-group 0
 !
 end-policy-map
!

Egress Policy:

At the egress, run these commands to mark the packets.

class-map match-any qos7
match qos-group 7
 end-class-map
!
class-map match-any qos6
match qos-group 6
 end-class-map
!
class-map match-any qos5
match qos-group 5
 end-class-map
!
class-map match-any qos4
match qos-group 4
 end-class-map
!
class-map match-any qos3
match qos-group 3
 end-class-map
!
class-map match-any qos2
 match qos-group 2
 end-class-map
!
class-map match-any qos1
match qos-group 1
 end-class-map
!

policy-map ncs_output
 class qos7
  set cos 7
  set dei 1
!
 class qos6
  set cos 6
  set dei 1
!
 class qos5
  set cos 5
  set dei 1
!
 class qos4
  set cos 4
  set dei 1
!
 class qos3
  set cos 3
  set dei 1
!
 class qos2
  set cos 2
  set dei 1

!
 class qos1
  set cos 1
  set dei 1
!
 end-policy-map
!

QoS L2 Re-Marking of Ethernet Packets on L3 Flows in Egress Direction on L3 sub-interfaces

The router supports Layer 2 marking of Ethernet packets on Layer 3 flows in the egress direction on L3 subinterfaces.

To enable this feature, you must:

Configure the policy maps for marking at the egress interface.
Ensure that the set qos-group command is configured in ingress policy and the corresponding match qos-group command is configured in the egress marking policy. If there is no corresponding QoS group, you experience traffic failure.

Restrictions

The following restrictions apply while configuring the Layer 2 marking of Ethernet packets on Layer 3 flows in the egress direction.

set discard-class is not supported in ingress policy with peering mode.
Egress marking statistics are not available.
Layer 2 (CoS, DEI) Egress marking is supported on Layer 3 flows on L3 subinterfaces for these types of traffic: IP-to-IP, IP-to-MPLS, and MPLS-to-IP traffic.

Running Configuration

Ingress Policy:

You must first set up the qos-group at ingress. This is applicable only when you want to mark packets at the egress.

class-map match-all COS0_DEI0
 match cos 0
 match dei 0
 end-class-map
class-map match-all COS0_DEI1
 match cos 0
 match dei 1
 end-class-map
class-map match-all COS1_DEI0
 match cos 1
 match dei 0
 end-class-map
class-map match-all COS1_DEI1
 match cos 1
 match dei 1
 end-class-map
class-map match-all COS2_DEI0
 match cos 2
 match dei 0
 end-class-map
class-map match-all COS2_DEI1
 match cos 2
 match dei 1
 end-class-map
class-map match-all COS3_DEI0
 match cos 3
 match dei 0
 end-class-map
class-map match-all COS3_DEI1
 match cos 3
 match dei 1
 end-class-map
class-map match-all COS4_DEI0
 match cos 4
 match dei 0
 end-class-map
class-map match-all COS4_DEI1
 match cos 4
 match dei 1
 end-class-map
class-map match-all COS5_DEI0
 match cos 5
 match dei 0
 end-class-map
class-map match-all COS5_DEI1
 match cos 5
 match dei 1
 end-class-map
class-map match-all COS6_DEI0
 match cos 6
 match dei 0
 end-class-map
class-map match-all COS6_DEI1
 match cos 6
 match dei 1
 end-class-map
class-map match-all COS7_DEI0
 match cos 7
 match dei 0
 end-class-map
class-map match-all COS7_DEI1
 match cos 7
 match dei 1
 end-class-map

policy-map ncs_input
 class COS7_DEI0
  set qos-group 7
  set discard-class 0
!
 class COS7_DEI1
  set qos-group 7
  set discard-class 1
!
 class COS6_DEI0
  set qos-group 6
  set discard-class 0
!
 class COS6_DEI1
  set qos-group 6
  set discard-class 1
!
 class COS5_DEI0
  set qos-group 5
  set discard-class 0
!
 class COS5_DEI1
  set qos-group 5
  set discard-class 1
!
 class COS4_DEI0
  set qos-group 4
  set discard-class 0
!
 class COS4_DEI1
  set qos-group 4
  set discard-class 1
!
 class COS3_DEI0
  set qos-group 3
  set discard-class 0
!
 class COS3_DEI1
  set qos-group 3
  set discard-class 1
!
 class COS2_DEI0
  set qos-group 2
  set discard-class 0
!
 class COS2_DEI1
  set qos-group 2
  set discard-class 1
!
 class COS1_DEI0
  set qos-group 1
  set discard-class 0
!
 class COS1_DEI1
  set qos-group 1
  set discard-class 1
!
 class COS0_DEI0
  set qos-group 0
  set discard-class 0
!
 class COS0_DEI1
  set qos-group 0
  set discard-class 1
!

Egress Policy:

At the egress, run these commands to mark the packets.

class-map match-all qos7_dc0
match qos-group 7
match discard-class 0
 end-class-map
!
class-map match-all qos7_dc1
match qos-group 7
match discard-class 1
 end-class-map
!

class-map match-all qos6_dc0
match qos-group 6
match discard-class 0
 end-class-map
!
class-map match-all qos6_dc1
match qos-group 6
match discard-class 1
 end-class-map
!
class-map match-all qos5_dc0
match qos-group 5
match discard-class 0
 end-class-map
!
class-map match-all qos5_dc1
match qos-group 5
match discard-class 1
 end-class-map
!
class-map match-all qos4_dc0
match qos-group 4
match discard-class 0
 end-class-map
!
class-map match-all qos4_dc1
match qos-group 4
match discard-class 1
 end-class-map
!
class-map match-all qos3_dc0
match qos-group 3
match discard-class 0
 end-class-map
!
class-map match-all qos3_dc1
match qos-group 3
match discard-class 1
 end-class-map
!
class-map match-all qos2_dc0
match qos-group 2
match discard-class 0
 end-class-map
!
class-map match-all qos2_dc1
match qos-group 2
match discard-class 1
 end-class-map
!
class-map match-all qos1_dc0
match qos-group 1
match discard-class 0
 end-class-map
!
class-map match-all qos1_dc1
match qos-group 1
match discard-class 1
 end-class-map
!
class-map match-all qos0_dc0
match qos-group 0
match discard-class 0
 end-class-map
!
class-map match-all qos0_dc1
match qos-group 0
match discard-class 1
 end-class-map
!


policy-map ncs_output
 class qos7_dc0
  set cos 7
  set dei 0
  set mpls experimental imposition 7
!
 class qos7_dc1
  set cos 7
  set dei 1
  set mpls experimental imposition 7
!
 class qos6_dc0
  set cos 6
  set dei 0
  set mpls experimental imposition 6
!
 class qos6_dc1
  set cos 6
  set dei 1
  set mpls experimental imposition 6
!
 class qos5_dc0
  set cos 5
  set dei 0
  set mpls experimental imposition 5
!
 class qos5_dc1
  set cos 5
  set dei 1
  set mpls experimental imposition 5
!
 class qos4_dc0
  set cos 4
  set dei 0
  set mpls experimental imposition 4
!
 class qos4_dc1
  set cos 4
  set dei 1
  set mpls experimental imposition 4
!
 class qos3_dc0
  set cos 3
  set dei 0
  set mpls experimental imposition 3
!
 class qos3_dc1
  set cos 3
  set dei 1
  set mpls experimental imposition 3
!
 class qos2_dc0
  set cos 2
  set dei 0
  set mpls experimental imposition 2
!
 class qos2_dc1
  set cos 2
  set dei 1
  set mpls experimental imposition 2
!
 class qos1_dc0
  set cos 1
  set dei 0
  set mpls experimental imposition 1
!
 class qos1_dc1
  set cos 1
  set dei 1
  set mpls experimental imposition 1
!
 class qos0_dc0
  set cos 0
  set dei 0
  set mpls experimental imposition 0
!
 class qos0_dc1
  set cos 0
  set dei 1
  set mpls experimental imposition 0
!
 end-policy-map
!

Bundle Traffic Policies

A policy can be bound to bundles. When a policy is bound to a bundle, the same policy is programmed on every bundle member (port). For example, if there is a policer or shaper rate, the same rate is configured on every port. Traffic is scheduled to bundle members based on the load balancing algorithm.

Both ingress and egress traffic is supported. Percentage-based policies , absolute rate-based policies, and time-based policies are supported.

Note

Egress marking is not supported on BVI interfaces.

For details, see Configure QoS on Link Bundles.

Shared Policy Instance

Table 3. Feature History Table
Feature Name	Release Information	Feature Description
Shared Policy Instance	Release 7.3.1	This feature allows you to share a single instance of QoS policy across multiple subinterfaces, allowing for aggregate shaping of the subinterfaces to one rate. The ability to facilitate queue consumption in this manner offers the advantage of saving on QoS and hardware resources, while ensuring that the specified rate is not exceeded.

Traditionally, when services required by your end-customers mapped one-on-one to an interface, attaching the QoS policy-map directly to the interface was the way to meet customer SLAs. However, with increasing demand for triple play configurations—requiring the management of voice and video queues in addition to data queues —you may have several forwarding constructs. This scenario calls for the need to apply an aggregate QoS policy across interfaces to provide the necessary traffic.

After you create the traffic class and traffic policy, you can optionally use a shared policy instance to allocate a single set of QoS resources and share them across a group of subinterfaces.

With shared policy instance, you can share a single instance of a QoS policy across multiple subinterfaces, allowing for aggregate shaping, policing, and marking of the subinterfaces to one rate. All the subinterfaces that share the instance of a QoS policy must belong to the same main interface. The number of subinterfaces that share the QoS policy instance can range from 2 to the maximum number of subinterfaces on the main interface.

When a shared policy instance of a policy map is shared by several subinterfaces, QoS operations such as aggregate shaping, policing, and marking are applied for traffic on all the interfaces that use the same shared policy instance.

Traditionally, policies were bound to interfaces. However, different types of interfaces, such as Layer 2 and Layer 3, can use a single shared-policy-instance, which allows flexibility in the "attachment point" that binds the policy map.

As an example, consider the following policy configuration:

policy-map hqos_gold
 class class-default
  service-policy child_hqos_gold
  shape average 20 mbps 
 ! 
 end-policy-map
! 
policy-map child_hqos_gold
 class voice
  priority level 1 
  shape average 64 kbps 
 ! 
 class video
  priority level 1 
  shape average 4 mbps 
 ! 
 class data
  bandwidth 5 mbps 
 ! 
 class class-default
 ! 
 end-policy-map
!

interface TenGigE 0/1/0/10.300 l2transport 
 service-policy output hqos_gold shared-policy-instance hqos_gold_customer1 
!
interface TenGigE 0/1/0/10.400 l2transport 
 service-policy output hqos_gold shared-policy-instance hqos_gold_customer1 
!

The keyword shared-policy-instance and the instance name hqos_gold_customer1 identify the subinterfaces that share an aggregate SLA. These are shared on a physical main interface or a bundle member. In other words, in a mix of Layer 2 and Layer 3 subinterfaces in the same shared policy instance, both layers support classification criteria and action.

In the case of bundles, sharing is applicable within a bundle member and not the entire bundle. Depending on the traffic hashing, shared policy instance may or may not take effect across the subinterface under the bundle main interface.

All subinterfaces that share the same shared policy instance share resources as well. Hence, the show policy-map statistics values and show qos values for all the subinterfaces are the same.

Restrictions and Guidelines

The following restrictions and guidelines apply while configuring shared policy instance for a policy map.

Subinterfaces that are part of the same shared policy must belong to the same main interface. In other words, subinterfaces of different main interfaces cannot be part of the same shared policy.
There is no restriction on the number of unique shared policies across a system. However, the limit of maximum number of subinterfaces with QoS policies applies.
There is no restriction on the number of unique shared policies per main interface, port, core, NPU, or line card.
You cannot use the same shared policy name on the ingress and egress of the same subinterface.
Shared policy instance is not supported with multi-policies. For example, on the egress, you cannot apply a marking policy and a queueing policy under a shared policy.
A shared policy can include a combination of Layer 2 and Layer 3 subinterfaces.

Attaching a Shared Policy Instance to Multiple Subinterfaces

To attach a shared policy instance to multiple subinterfaces:

Enter interface configuration mode and configure a subinterface.
Attach a policy map to an input or output subinterface for it to be the service policy for that subinterface.


RP/0/RP0/CPU0:router(config)#interface HundredGigE0/3/0/0.1
RP/0/RP0/CPU0:router(config-subif)#service-policy output pm-out shared-policy-instance spi1

Running Configuration

interface HundredGigE0/3/0/0.1
service-policy output pm-out shared-policy-instance spi1
ipv4 address 20.0.0.1 255.255.255.0
encapsulation dot1q 1
!

Verification

The show policy-map shared-policy-instance command includes an option to display counters for the shared policy instance.

Note

For bundle subinterfaces, use RP as the location keyword.
For physical subinterfaces, use LC as the location keyword.

For example, for a physical interface:

RP/0/RP0/CPU0:ios#show policy-map shared-policy-instance spi1 output location 0/3/CPU0 

Shared Policy Instance spi1 output: pm-out

Class cm-tc-1
  Classification statistics          (packets/bytes)               (rate - kbps)
    Matched             :           772637560/1143503679080        9622860
    Transmitted         :           731260312/1082265352040        5052880
    Total Dropped       :            41377248/61238327040          4569980
  Queueing statistics
    Queue ID                             : 1433 
    Taildropped(packets/bytes)           : 41377248/61238327040
Class class-default
  Classification statistics          (packets/bytes)     (rate - kbps)
    Matched             :                   0/0                    0
    Transmitted         :                   0/0                    0
    Total Dropped       :                   0/0                    0
  Queueing statistics
    Queue ID                             : 1432 
    Taildropped(packets/bytes)           : 0/0
Policy Bag Stats time: 1604675533816  [Local Time: 11/06/20 15:12:13.816]

Use the clear qos counters shared-policy-instance command to clear counters for the shared policy instance.

Note

For bundle subinterfaces, use RP as the location keyword.
For physical subinterfaces, use LC as the location keyword.

For example, for a physical interface:

RP/0/RP0/CPU0:ios#clear qos counters shared-policy-instance spi1 output location 0/3/CPU0

The show qos shared-policy-instance command allows you to display the QoS hardware programming values.

Note

For bundle subinterfaces, use RP as the location keyword.
For physical subinterfaces, use LC as the location keyword.

For example, for a physical interface:

RP/0/RP0/CPU0:ios#show qos shared-policy-instance spi1 output location 0/3/CPU0 
Fri Nov  6 15:21:44.200 UTC
NOTE:- Configured values are displayed within parentheses
Interface HundredGigE0/3/0/0.1 ifh 0x60040c8  -- output policy
NPU Id:                        0
Total number of classes:       2
Interface Bandwidth:           100000000 kbps
Policy Name:                   pm-out
SPI Id:                        0x3000001
VOQ Base:                      1432
Accounting Type:               Layer1 (Include Layer 1 encapsulation and above)
------------------------------------------------------------------------------
Level1 Class                             =   cm-tc-1
Egressq Queue ID                         =   1433 (LP queue)
Queue Max. BW.                           =   5118857 kbps (5 %)
Queue Min. BW.                           =   0 kbps (default)
Inverse Weight / Weight                  =   1 / (BWR not configured)
Guaranteed service rate                  =   5000000 kbps
Peak burst                               =   33600 bytes (default)
TailDrop Threshold                       =   6258688 bytes / 10 ms (default)
WRED not configured for this class

Level1 Class                             =   class-default
Egressq Queue ID                         =   1432 (Default LP queue)
Queue Max. BW.                           =   no max (default)
Queue Min. BW.                           =   0 kbps (default)
Inverse Weight / Weight                  =   1 / (BWR not configured)
Guaranteed service rate                  =   50000000 kbps
Peak burst                               =   33600 bytes (default)
TailDrop Threshold                       =   62652416 bytes / 10 ms (default)
WRED not configured for this class

Ingress Short-Pipe

When QoS traffic leaves an MPLS network, the MPLS label stack is removed on the penultimate ingress Label Switch Router (LSR), leaving an IPv4 or IPv6 packet to be forwarded. MPLS experimental bits (or EXP or pipe mode) carries out this disposition process and the packet is marked with a Differentiated Services Code Point (DSCP) or precedence value (also called DSCP or Precedence-based classification).

Usually, QoS traffic supports DSCP and precedence-based classifications only when there is no MPLS label in the packet. Using the ingress short-pipe feature, however, you can classify a packet that contains one MPLS label using the type-of-service (ToS) field of the IPv4 or IPv6 header. This classification method is called ingress short-pipe. To classify an IP packet this way, you must:

Create a child class map.
Specify a ToS value in the child class map.
Attach the child class map to a parent class map.
Create a policy map containing the parent class map.
Set any ingress action such as traffic class or QoS group. From Release 7.1.1 onwards, you can also set ingress action DSCP (or precedence value).

With the ingress short-pipe feature, you get an increased visibility into traffic packets. Plus, the feature also removes the limitation of classifying MPLS packets that come into IPv4 or IPv6 networks.

Restrictions and Other Important Points

Ensure that you read these points before you configure the ingress short-pipe feature.

This feature isn’t supported on:
- NC57-24DD
- NC57-18DD-SE
- NC57-36H-SE
- NC57-36H6D-S
- NC57-MOD-S
- NCS-57B1-6D24-SYS
- NCS-57B1-5DSE-SYS
- NCS-57C3-MOD-SYS
- NCS-57D2-18DD-SYS
This feature works only when there is one MPLS header in the traffic packet. If there are two or more MPLS headers, the ingress-short pipe feature fails. For example, in case of Explicit Null where there are two labels at the disposition, this feature will not work.
You can carry out ingress classification using either the MPLS experimental bits (or EXP or pipe mode) classification OR the DSCP/precedence (or short-pipe) classification. Ensure that you do not mix the classification methods, else it may result in an unknown behavior, and the classification may not work at all.
This feature is supported only on L3VPN, and not supported on L2VPN.
This feature works for regular IPv4/IPv6 traffic, but will not work for IPv6 VPN Provider Edge over MPLS (6VPE).
You can add only one child class map to a parent class map.
This feature supports the invocation of short-pipe and legacy DSCP classification for the same parent class map.
The child class map can contain only match precedence and match dscp commands.
This feature is not supported in peering mode.

Configure Ingress Short-Pipe

This section details a sample configuration for the ingress short-pipe feature and another sample to configure classification for labeled and non-labeled packets under the same parent class.

Sample configuration to classify a packet that contains one MPLS label using the type-of-service (ToS) field of the IPv4 or IPv6 header (or the ingress short-pipe method):

class-map match-any in_pipe
 match mpls disposition class-map child_pipe 
end-class-map
!
class-map match-any child_pipe
 match precedence 1 
match dscp ipv4 af11
 end-class-map
!
class-map match-any ingress-business-high
match dscp af21 af22
end-class-map

class-map match-any ingress-business-low
match dscp af11 af12
end-class-map

policy-map ingress-classifier
class in_pipe
set traffic-class 5
set dscp af31
class ingress-business-high
set traffic-class 4
class ingress-business-low
set traffic-class 2
class class-default
set traffic-class 0
!

Note

The set dscp option is available from Release 7.1.1 onwards.

You can configure classification for both labeled and non-labeled packets under the same parent class as in the following sample configuration. In this example, for MPLS labeled packets, DSCP configured under the child class is classified, while for non-labeled packets, DSCP/ToS configured in the match dscp <value> statement is classified.

DSCP value range is from 0 through 63. The range option is not supported. Up to 8 items per class are supported. Up to 64 match dscp values in total.

class-map match-any in_pipe
match mpls disposition class-map child_pipe  (labeled case)
match dscp af11 (non-labeled case)
end-class-map
!
class-map match-any child_pipe
match precedence 1 
match dscp ipv4 af11
end-class-map
!
class-map match-any ingress-business-high
match dscp af21 af22
end-class-map
 
class-map match-any ingress-business-low
match dscp af11 af12
end-class-map
 
policy-map ingress-classifier
class in_pipe
set traffic-class 5

class ingress-business-high
set traffic-class 4
class ingress-business-low
set traffic-class 2
class class-default
set traffic-class 0
!

Associated Commands

match mpls disposition class-map

Selective Egress Policy-Based Queue Mapping

With selective egress policy-based queue mapping, you can combine traffic class (TC) maps in various permutations at the egress.

Note

Modular chassis do not support this feature.

The primary aim of introducing the egress TC (traffic class) mapping is to classify the traffic in the ingress using a single policy and place the classified traffic into queues, by assigning the traffic classes. At the egress, you can support different groupings of TCs.

Based on different Service Level Agreements (SLAs) that each customer has signed up for, you can group some TCs into priority queues for real time (RT) traffic, other TCs into guaranteed bandwidth (BW) traffic, and the rest into best effort (BE) traffic delivery.

Let us consider an example where three customers have purchased these services, based on their requirements:

Customer A - Requires RT traffic, reserved BW traffic and BE traffic delivery.
Customer B – Requires reserved BW traffic and BE traffic delivery.
Customer C – Needs only BE traffic delivery.

Using the selective egress policy-based queue mapping, you can create three profiles this way:

Customer A – Priority queue RT traffic (TC1), Guaranteed BW traffic (TC3), Best effort traffic (TC0, TC5)
Customer B – Guaranteed BW traffic (TC1), Best effort traffic (TC0, TC3, TC5)
Customer C - Best effort traffic (TC0, TC1, TC3, TC5)

Using the egress TC-mapping, you can create three different profiles that you can use for each customer based on their SLAs with the provider.

Figure 1. Selective Egress Policy-Based Queue Mapping Helps Create Customer Profiles Based on Their SLAs

Restrictions and Other Important Points

Ensure that you read these points before you configure the selective egress policy-based queue-mapping feature.
- There can be only one TC (Traffic Class) mapped class to a PM (Policy Map).
- You cannot use a TC that you used in a mapped class, in a non-mapped class under the same PM.
- You can have a maximum of three unique TC mapped PMs or profiles per platform.
- Every TC mapped class must include traffic-class 0 in the range values.
- The TC-mapping range is from 0 through 5.
- When a TC-mapped class is present in a PM, the class default becomes a dummy class. This means that the class default statistics and QoS values are not applicable.
- All the class default limitations apply to the TC-mapped class; for example, you cannot configure priority command under the TC mapped class.

Note

A TC-mapped PM or profile is a PM that contains a TC-mapped class.

Example of a TC-mapped class:

match traffic-class 0 1 2 3

Example of a TC non-mapped class:

match traffic-class 1

Configure Selective Egress Policy-Based Queue Mapping

This section details a sample configuration for the selective egress policy-based queue-mapping feature and a use case to show how this feature works.

Sample configuration


class-map match-any <name>
 match traffic-class <value>
commit

policy-map tc_pmap
 class tc035
  shape average percent 1 
 ! 
 class class-default
! 
 end-policy-map
! 
 class-map match-any tc035
match traffic-class 0 3 5 
 end-class-map
!

Verification

Run the show qos interface and show policy-map interface commands.

When TC mapping class is present in a policy map, the class default does not have any values calculated.

show qos interface bundle-Ether 44 output sample

NOTE:- Configured values are displayed within parentheses
NPU Id:                        0
Total number of classes:       3
Interface Bandwidth:           100000000 kbps
Policy Name:                   tc_pmap
Accounting Type:               Layer1 (Include Layer 1 encapsulation and above)
------------------------------------------------------------------------------
Level1 Class                             =   tc1
 
Level1 Class                             =   tc035
 
Level1 Class                             =   class-default
 
Interface HundredGigE0/0/0/30 Ifh 0xf000208 (Member) -- output policy
NPU Id:                        0
Total number of classes:       3
Interface Bandwidth:           100000000 kbps
Policy Name:                   tc_pmap
VOQ Base:                      1264
Accounting Type:               Layer1 (Include Layer 1 encapsulation and above)
------------------------------------------------------------------------------
Level1 Class                             =   tc1
Egressq Queue ID                         =   1265 (LP queue)
Queue Max. BW.                           =   10063882 kbps (10 %)
Queue Min. BW.                           =   0 kbps (default)
Inverse Weight / Weight                  =   1 / (BWR not configured)
Guaranteed service rate                  =   10000000 kbps
TailDrop Threshold                       =   12517376 bytes / 10 ms (default)
WRED not configured for this class
 
Level1 Class                             =   tc035
Egressq Queue ID                         =   1264 (LP queue)
Queue Max. BW.                           =   1011732 kbps (1 %)
Queue Min. BW.                           =   0 kbps (default)
Inverse Weight / Weight                  =   1 / (BWR not configured)
Guaranteed service rate                  =   1000000 kbps
TailDrop Threshold                       =   1253376 bytes / 10 ms (default)
WRED not configured for this class
 
Level1 Class                             =   class-default
Queue Max. BW.                           =   no max (default)
Queue Min. BW.                           =   0 kbps (default)
Inverse Weight / Weight                  =   0 / (BWR not configured)

show policy-map interface bundle-Ether 44 output sample

Bundle-Ether44 output: tc_pmap
 
Class tc1
  Classification statistics          (packets/bytes)     (rate - kbps)
    Matched             :              429444/53823648             0
    Transmitted         :              429444/53823648             0
    Total Dropped       :                   0/0                    0
  Queueing statistics
    Queue ID                             : None (Bundle)
    Taildropped(packets/bytes)           : 0/0
Class tc035
  Classification statistics          (packets/bytes)     (rate - kbps)
    Matched             :             1288331/161470820            0
    Transmitted         :             1288331/161470820            0
    Total Dropped       :                   0/0                    0
  Queueing statistics
    Queue ID                             : None (Bundle)
    Taildropped(packets/bytes)           : 0/0
Class class-default
  Classification statistics          (packets/bytes)     (rate - kbps)
    Matched             :                   0/0                    0
    Transmitted         :                   0/0                    0
    Total Dropped       :                   0/0                    0
  Queueing statistics
    Queue ID                             : None (Bundle)
    Taildropped(packets/bytes)           : 0/0
Policy Bag Stats time: 1557216940000  [Local Time: 05/07/19 08:15:40.000]
RP/0/RP0/CPU0:BB1#

Use Case

With the ingress traffic matching the same match criteria, you can group the egress traffic up to three unique TC mapped profiles. Using this feature, you can provide differentiated services to customers based on the SLAs they have signed up for.

In the example that follows, the ingress policy-map sets the ingress match criteria for the traffic class from 0 through 5. Based on the SLAs, you can group the TC values at the egress PM to deliver differentiated services.

After you group the TC values, you can apply specific egress actions under that class.

Ingress match:

class EXP1
  set traffic-class 1
!
class EXP2
  set traffic-class 2
!
class EXP3
  set traffic-class 3
!
class EXP4
  set traffic-class 4
!
class EXP5
  set traffic-class 5
!
class class-default
!
end-policy-map
!

Egress match:

Sample TC mapped class for policy-map PM1

class-map match-any TC2:1
match traffic-class 0 1
end-class-map

Sample TC mapped class for policy-map PM2

class-map match-any TC3:1
match traffic-class 0 1 2
end-class-map

Sample TC mapped class for policy-map PM3

class-map match-any TC6:1
match traffic-class 0 1 2 3 4 5
end-class-map

Configuring QoS Groups with an ACL

You can create QoS groups and configure ACLs to classify traffic into the groups based on a specified match condition. In this example, we match by the QoS group value (0-511).

Supported ACL Types

Your router supports the following ACL types.

Note

If you configure QoS group with an unsupported ACL type, the system doesn’t display any error message.


ACL Type	Example
IPv4 DSCP	permit ipv4 any any dscp af43
UDP DSCP	permit udp any any dscp af43
UDP Fragments IPv4	udp any any fragments - IPv4
UDP Fragments IPv6	udp any any fragments - IPv6
TCP Fragments IPv4	tcp any any fragments - IPv4
TCP Fragments IPv6	tcp any any fragments - IPv6
IPV4 DSCP Fragments	permit ipv4 any any dscp af43 fragments
UDP DSCP Fragments	permit udp any any dscp af43 fragments
UDP Host Fragments	permit udp host <sip> host <dip> fragments
TCP Host Fragments	permit tcp host <sip> host <dip> dscp af43 fragments
TCP DSCP	permit tcp <source network > <destination network> dscp af43
TCP Port based	permit tcp any any eq <port>
UDP Port based	permit udp any any eq <port>
TCP Flags	permit tcp host <sip> host <dip> established fin psh syn urg

Restrictions

ACLs with fragment match are supported on systems with only NC57 line cards, also referred to as native mode.

IPv6 ACLs with fragment match are supported only in short and short-l2-qos mode.

Prerequisites

Before you can configure QoS groups with an ACL, the QoS peering profile must be enabled on the router or the line card. After enabling QoS peering, the router or line card must be reloaded, as shown in the following configuration.

Enabling QoS Peering Profile on the Router

Enter the global configuration mode and enable the QoS peering profile for the router as shown:

RP/0/RP0/CPU0:router(config)# hw-module profile qos ingress-model peering 
RP/0/RP0/CPU0:router(config)# exit
RP/0/RP0/CPU0:router# reload

Enabling QoS Peering Profile on the Line Card

Enter the global configuration mode and enable the QoS peering profile for the line card as shown:

RP/0/RP0/CPU0:router(config)# hw-module profile qos ingress-model peering location 0/0/CPU0
RP/0/RP0/CPU0:router(config)# exit
RP/0/RP0/CPU0:router# reload location 0/0/CPU0

Configuration

Use the following set of configuration statements to configure an ACL with QoS groups.


/*
 Enter the global configuration mode, and configure an ACL with the required QoS groups. */
RP/0/RP0/CPU0:router# configure
RP/0/RP0/CPU0:router(config)# ipv4 access-list qos-acl
RP/0/RP0/CPU0:router(config-ipv4-acl)# 10 permit ipv4 host 5.0.0.1 any set qos-group 1
RP/0/RP0/CPU0:router(config-ipv4-acl)# 11 permit ipv4 host 6.0.0.1 any set qos-group 2 
RP/0/RP0/CPU0:router(config-ipv4-acl)# 12 permit ipv4 host 7.0.0.1 any set qos-group 3
RP/0/RP0/CPU0:router(config-ipv4-acl)# 13 deny ipv4 any any


/* Create a policy map with the required classes.
In this example, we also create a default class for traffic that does not belong to any of the specified
classes. */
RP/0/RP0/CPU0:router(config)# policy-map qos-acl-map 
RP/0/RP0/CPU0:router(config-pmap)# class qos1
RP/0/RP0/CPU0:router(config-pmap-c)# set dscp af43
RP/0/RP0/CPU0:router(config-pmap-c)# set traffic-class 2
RP/0/RP0/CPU0:router(config-pmap-c)# exit

RP/0/RP0/CPU0:router(config-pmap)# class qos2
RP/0/RP0/CPU0:router(config-pmap-c)# set precedence critical
RP/0/RP0/CPU0:router(config-pmap-c)# set traffic-class 7
RP/0/RP0/CPU0:router(config-pmap-c)# exit

RP/0/RP0/CPU0:router(config-pmap)# class qos3
RP/0/RP0/CPU0:router(config-pmap-c)# set precedence 2
RP/0/RP0/CPU0:router(config-pmap-c)# set traffic-class 2
RP/0/RP0/CPU0:router(config-pmap-c)# exit 

RP/0/RP0/CPU0:router(config-pmap)# class qos4
RP/0/RP0/CPU0:router(config-pmap-c)# set traffic-class 4
RP/0/RP0/CPU0:router(config-pmap-c)# set dscp cs4
RP/0/RP0/CPU0:router(config-pmap-c)# exit

RP/0/RP0/CPU0:router(config-pmap)# class class-default 
RP/0/RP0/CPU0:router(config-pmap-c)# police rate percent 20
RP/0/RP0/CPU0:router(config-pmap-c-police)# exit


/* Create the class maps for specifying the match conditions. */
RP/0/RP0/CPU0:router(config)# class-map match-any qos1
RP/0/RP0/CPU0:router(config-cmap)# match qos-group 1
RP/0/RP0/CPU0:router(config-cmap)# end-class-map
 
RP/0/RP0/CPU0:router(config)# class-map match-any qos2
RP/0/RP0/CPU0:router(config-cmap)#  match qos-group 2
RP/0/RP0/CPU0:router(config-cmap)# end-class-map 

RP/0/RP0/CPU0:router(config)# class-map match-any qos3
RP/0/RP0/CPU0:router(config-cmap)# match qos-group 3
RP/0/RP0/CPU0:router(config-cmap)# end-class-map 

RP/0/RP0/CPU0:router(config)# class-map match-any qos4
RP/0/RP0/CPU0:router(config-cmap)# match qos-group 4
RP/0/RP0/CPU0:router(config-cmap)# end-class-map 


/* Apply the access list and the QoS map to the Gigabit interface, and commit your configuration. */
RP/0/RP0/CPU0:router(config)# interface TenGigE0/0/0/1
RP/0/RP0/CPU0:router(config-if)# ipv4 address 12.0.0.1/24
RP/0/RP0/CPU0:router(config-if)# no shut
RP/0/RP0/CPU0:router(config-if)# service-policy input qos-acl-map
RP/0/RP0/CPU0:router(config-if)# ipv4 access-group qos-acl ingress compress level 3

RP/0/RP0/CPU0:router(config-if)# commit             
Tue Mar 28 10:23:34.106 IST
 
RP/0/0/CPU0:Mar 28 10:37:48.570 : ifmgr[397]: %PKT_INFRA-LINK-3-UPDOWN : Interface TenGigE0/0/0/1, changed state to Down 
RP/0/0/CPU0:Mar 28 10:37:48.608 : ifmgr[397]: %PKT_INFRA-LINK-3-UPDOWN : Interface TenGigE0/0/0/1, changed state to Up 

RP/0/RP0/CPU0:router(config-if)# exit

Running Configuration

Confirm your configuration.

RP/0/RP0/CPU0:router(config)# show run
Tue Mar 28 10:37:55.737 IST

Building configuration...
!! IOS XR Configuration 0.0.0

ipv4 access-list qos-acl
10 permit ipv4 host 5.0.1.1 any set qos-group 1
11 permit ipv4 host 6.0.1.1 any set qos-group 2
12 permit ipv4 host 7.0.1.1 any set qos-group 3
13 deny ipv4 any any 
 
class-map match-any qos1
match qos-group 1
end-class-map
!
class-map match-any qos2
match qos-group 2
end-class-map
!
class-map match-any qos3
match qos-group 3
end-class-map
!
class-map match-any qos4
match qos-group 4
end-class-map
!
 
policy-map qos-acl-map
class qos1
  set dscp af43
  set traffic-class 2
!
class qos2
  set precedence critical
  set traffic-class 7
!
class qos3
  set precedence 2
  set traffic-class 2
!
class qos4
  set traffic-class 4
  set dscp cs4
!
class class-default
  police rate percent 20
  !
!
end-policy-map
!
 
interface TenGigE0/0/0/1
service-policy input qos-acl-map
ipv4 address 12.0.0.1 255.255.255.0
ipv4 access-group qos-acl ingress compress level 3

!

You have successfully configured an ACL with QoS groups.

Configuring an ACL with Fragment Match

Usually, IP ACLs process non-fragmented packets and the first fragments of a packet using permit and deny actions. These packets may have Layer 3 and 4 information that the ACLs match for a permit or deny action. By default, however, ACLs permit noninitial fragments. This could lead to potential security issues with users with malicious intent using the noninitial fragments to launch denial of service (DoS) attacks.

With this feature, you can now to set QoS policies for noninitial fragment packets, thus having more granular control over noninitial IP fragments of a packet. Noninitial IP fragments have the fragment offset value non-zero. To know more about fragments, see the IP Addresses and Services Configuration Guide for Cisco NCS 5500 Series Routers.

Restrictions and Guidelines

The following restrictions and guidelines apply while configuring an ACL with fragment match.

To enable IPv6 fragment classification support, configure hw-module profile qos ipv6 short-l2qos-enable or hw-module profile qos ipv6 short .
IPv6 fragmentation is supported with only one Extension Header (EH).

Configuring an ACL with Fragment Match

For IPv4 and IPv6 ACLs

To configure an ACL with fragment match, you must:

Create IPv4 and IPv6 ACLs with fragment match.

Note

To enable IPv6 fragment classification support, configure hw-module profile qos ipv6 short-l2qos-enable or hw-module profile qos ipv6 short .

Create two class maps, one for IPv4 and IPv6, and attach the respective ACLs to the class maps.
Create a policy map with these two class maps and set action.

Router(config)#ipv4 access-list v4_ace
Router(config-ipv4-acl)#permit ipv4 any any fragments
Router(config-ipv4-acl)#exit
Router(config)#
Router(config)#ipv6 access-list v6_ace
Router(config-ipv6-acl)#permit ipv6 any any fragments
Router(config-ipv6-acl)#exit
Router(config)# 
Router(config)#class-map match-any v4_class
Router(config-cmap)#match access-group ipv4 v4_ace
Router(config-cmap)#exit
Router(config)#
Router(config)#class-map match-any v6_class
Router(config-cmap)#match access-group ipv6 v6_ace
Router(config-cmap)#exit
Router(config)#policy-map frag_policy
Router(config-pmap)#class v4_class
Router(config-pmap-c)#set traffic-class 3
Router(config-pmap-c)#police rate 100 mbps
Router(config-pmap-c-police)#exit
Router(config-pmap-c)#
Router(config-pmap-c)#class v6_class
Router(config-pmap-c)#police rate 150 mbps peak-rate 200 mbps
Router(config-pmap-c-police)#exit 
Router(config-pmap-c)#exit
Router(config-pmap)#exit

Running Configuration

ipv4 access-list v4_ace
 permit ipv4 any any fragments
 exit
!
ipv6 access-list v6_ace
 permit ipv6 any any fragments
 exit
!
class-map match-any v4_class
 match access-group ipv4 v4_ace
 exit
!
class-map match-any v6_class
 match access-group ipv6 v6_ace
 exit
 
policy-map frag_policy
 class v4_class
  set traffic-class 3
  police rate 100 mbps
   exit
!
 class v6_class
  police rate 150 mbps peak-rate 200 mbps

Verification

Run the show policy-map pmap-name frag_policy detail command to confirm the ACL fragment matches and the show qos int hundredGigE 0/5/0/2 input command to confirm the policer details.

Router#show policy-map pmap-name frag_policy detail
ipv4 access-list v4_ace
10 permit ipv4 any any fragments
 
ipv6 access-list v6_ace
10 permit ipv6 any any fragments
 
class-map match-any v4_class
match access-group ipv4 v4_ace
 end-class-map
!
class-map match-any v6_class
match access-group ipv6 v6_ace
 end-class-map
!
policy-map frag_policy
class v4_class
  set traffic-class 3
  police rate 100 mbps
  !
 !
 class v6_class
  police rate 150 mbps peak-rate 200 mbps
  !
 !
 class class-default
!
 end-policy-map
!
 
Router#show qos int hundredGigE 0/5/0/2 input
NOTE:- Configured values are displayed within parentheses
Interface HundredGigE0/5/0/2 ifh 0xa000088  -- input policy
NPU Id:                        0
Total number of classes:       3
Interface Bandwidth:           100000000 kbps
Policy Name:                   frag_policy
SPI Id:                        0x0
Accounting Type:               Layer2 (Include Layer 2 encapsulation and above)
------------------------------------------------------------------------------
Level1 Class                             =   v4_class
New traffic class                        =   3
 
Policer Bucket ID                        =   0x12
Policer Stats Handle                     =   0x0
Policer committed rate                   =   99609 kbps (100 mbits/sec)
Policer conform burst                    =   124672 bytes (default)
 
Level1 Class                             =   v6_class
 
Policer Bucket ID                        =   0x11
Policer Stats Handle                     =   0x0
Policer committed rate                   =   150390 kbps (150 mbits/sec)
Policer peak rate                        =   200195 kbps (200 mbits/sec)
Policer conform burst                    =   186624 bytes (default)
Policer exceed burst                     =   436096 bytes (default)
 
Level1 Class                             =   class-default
 
Default Policer Bucket ID                =   0x10
Default Policer Stats Handle             =   0x0
Policer not configured for this class

Restrictions

Refer to the following table for Ingress QoS Scale limitation.

Table 4. Ingress QoS Scale Limitation
QoS Mode	Class-Map Size	Maximum number of Interfaces with Ingress QoS Applied
QoS Mode	Class-Map Size	Per Core	Per NPU
Normal	4	1023	2046
Normal	8	511	1022
Normal	16	255	510
Normal	32	127	254
Enhanced	4	871	1742
Enhanced	8	435	870
Enhanced	16	217	434
Enhanced	32	108	216

Note

If you apply an ingress policy map to a bundle that has bundle members only from a single core of an NPU, the QoS resources are consumed on both cores of that NPU.

Example: For Default Configuration, which is Normal (2 counter mode) QoS Mode & 32 Class Map-Size, you can configure 191 interfaces with Ingress Policy per core.

Other restrictions to follow:

If you have a set traffic class statement explicitly configured in the ingress service policy, it’s mandatory to have a corresponding match traffic class on egress for the traffic to be correctly matched and the stats to be accounted in show policy-map interface <> output command. To match the ingress traffic to the egress class-default, traffic class should be set to 0 on ingress.
If you have a set traffic class that is configured in ingress service policy, and no corresponding match traffic class on egress, the traffic won’t go to class default and the stats for this traffic flow won’t be seen in show policy-map interface <> output command.
If you don’t have any set traffic class statement in ingress, then traffic will hit the default-class on egress.
If you have a set discard-class statement configured in the ingress service policy, it’s mandatory to have a corresponding match discard-class on egress for the traffic to be correctly matched and the stats to be accounted in show policy-map interface <> output command.
If you have a set discard-class statement configured in the ingress service policy and don’t have a corresponding match discard-class on egress, the traffic won’t hit the class-default and the stats for this flow won’t be accounted in show policy-map interface <> output command.
The system doesn’t support class-map size on peering mode.
Even if you have an egress policy that has the drop action configured, the transmitted counter stats still shows an increment.
Depending on the packet size, the traffic shaped value for low shaper rates, such as 10mbps, have greater deviation than 5% of tolerance from the shaper value. For higher shaper rates, the deviation is within the limit of 5% of tolerance from the shaper value for all packet sizes.
If the shaper rate is less than 7 Mbps, the calculation of queue-limit is based on 10 ms of guaranteed service rate, and which leads to different queue-limit for each shaper value. This consumes the rate-profile for each queue-limit, and can also lead to a queue-limit of less than 1 MTU causing larger packets to drop.

Restrictions for Peering QoS Profile

After enabling the QoS peering feature using the hw-module profile qos ingress-model peering command, you can set the Layer 2 class of service (CoS) or drop eligible indicator (DEI) values at the egress using the set cos or set dei commands, respectively. However, at the egress, ensure that you don’t set the MPLS experimental imposition (EXP) values (using the set mpls experimental imposition command). Otherwise, when committing the policy map with these configurations at the egress, you will encounter an error. This error occurs because the internal fields required for egress EXP marking are not available with peering enabled.
explicit set discard-class statement isn’t supported.
This feature is supported only on L3 interfaces and is limited to 1000 L3 interfaces per system.
set mpls exp topmost statement isn’t supported within QoS in peering mode.
access group statement isn’t supported.
(Only in Release 6.2.x and Release 6.3.x) set mpls exp imposition statement isn’t supported on ingress interface.
2-Level ingress policers isn’t supported.
(From Release 6.5.x) Egress H-QOS with peering profile support is enabled, but ingress H-QOS with peering profile isn’t supported.
Depending on the packet size, the traffic shaped value for low shaper rates, such as 10mbps, have greater deviation than 5% of tolerance from the shaper value. For higher shaper rates, the deviation is within the limit of 5% of tolerance from the shaper value for all packet sizes.
(From Release 7.2.1) On NC57 line cards, QoS ingress peering profile isn’t supported. This restriction is applicable for systems operating in compatibility mode and native mode.

Restrictions for QoS on BVI

The system doesn’t support the egress policy on Bridge-Group Virtual Interface (BVI), but BVI (CoS, DEI) marking is supported by applying the policy to its corresponding Layer 2 interface, which is part of the same bridge domain.
If you apply L3 ingress QoS policy on L2 interface, which is a part of the same bridge-domain as BVI, the classification might not work if packets are destined to the BVI MAC address.
If a QoS policy is attached to BVI, the policy is inherited by the L2 interfaces, which are part of the same bridge-domain. Hence, any other policy can’t be applied on the L2 interfaces. Similarly, if a QoS policy is attached to any of the L2 interfaces, any QoS policy can’t be applied on the BVI, which is part of the same bridge-domain.
In the two-pass forwarding model for packets from Layer 2 to Layer 3 over BVI, where Layer 2 and Layer 3 forwarding are split across two paths and packet processing happens in two cycles, you can apply separate QoS policies for Layer 2 and BVI interfaces.

Restrictions for Egress Drop Action

A maximum of 8 interfaces can have the drop action configured and a maximum of 8 classes in any single policy can have the drop action.
A drop action in any particular class can’t be combined with other actions.
Drop action in a policy applied on the main interface isn’t inherited onto sub-interfaces.
Match condition for drop action PM can only be based on qos-group, discard class based match isn’t supported.

In-Place Policy Modification

The In-Place policy modification feature allows you to modify a QoS policy even when the QoS policy is attached to one or more interfaces. A modified policy is subjected to the same checks that a new policy is subject to when it is bound to an interface. If the policy-modification is successful, the modified policy takes effect on all the interfaces to which the policy is attached. However, if the policy modification fails on any one of the interfaces, an automatic rollback is initiated to ensure that the pre-modification policy is in effect on all the interfaces.

You can also modify any class map used in the policy map. The changes made to the class map take effect on all the interfaces to which the policy is attached.

Note

The QoS statistics for the policy that is attached to an interface are lost (reset to 0) when the policy is modified.
When a QoS policy attached to an interface is modified, there might not be any policy in effect on the interfaces in which the modified policy is used for a short period of time.
The system does not support the show policy-map statistics for marking policies.
An in-place modification of an ACL does not reset the policy-map statistics counter.

Note

For QOS EXP-Egress marking applied on a Layer 3 interface on Cisco NCS550x and NCS55Ax routers, there is a limit of two unique policy-maps per NPU. This limit is three unique policy maps per NPU for routers that have the Cisco NC57 line cards installed. When the maximum limit for policy-maps is reached and you try to modify a policy-map which is shared between different interfaces, you may get an error.
For QOS egress marking (CoS, DEI) applied on a Layer 2 interface, there is a limit of 13 unique policy-maps per NPU. When the maximum limit for policy-maps is reached and you try to modify a policy-map which is shared between different interfaces, you may get an error.

Verification

If unrecoverable errors occur during in-place policy modification, the policy is put into an inconsistent state on target interfaces. No new configuration is possible until the configuration session is unblocked. It is recommended to remove the policy from the interface, check the modified policy and then re-apply accordingly.

Specification of the CoS for a Packet with IP Precedence

Use of IP precedence allows you to specify the CoS for a packet. You can create differentiated service by setting precedence levels on incoming traffic and using them in combination with the QoS queuing features. So that, each subsequent network element can provide service based on the determined policy. IP precedence is usually deployed as close to the edge of the network or administrative domain as possible. This allows the rest of the core or backbone to implement QoS based on precedence.

Figure 2. IPv4 Packet Type of Service Field

You can use the three precedence bits in the type-of-service (ToS) field of the IPv4 header for this purpose. Using the ToS bits, you can define up to eight classes of service. Other features configured throughout the network can then use these bits to determine how to treat the packet in regard to the ToS to grant it. These other QoS features can assign appropriate traffic-handling policies, including congestion management strategy and bandwidth allocation. For example, queuing features such as LLQ can use the IP precedence setting of the packet to prioritize traffic.

IP Precedence Bits Used to Classify Packets

Use the three IP precedence bits in the ToS field of the IP header to specify the CoS assignment for each packet. You can partition traffic into a maximum of eight classes and then use policy maps to define network policies in terms of congestion handling and bandwidth allocation for each class.

Each precedence corresponds to a name. IP precedence bit settings 6 and 7 are reserved for network control information, such as routing updates. These names are defined in RFC 791.

IP Precedence Value Settings

By default, the routers leave the IP precedence value untouched. This preserves the precedence value set in the header and allows all internal network devices to provide service based on the IP precedence setting. This policy follows the standard approach stipulating that network traffic should be sorted into various types of service at the edge of the network and that those types of service should be implemented in the core of the network. Routers in the core of the network can then use the precedence bits to determine the order of transmission, the likelihood of packet drop, and so on.

Because traffic coming into your network can have the precedence set by outside devices, we recommend that you reset the precedence for all traffic entering your network. By controlling IP precedence settings, you prohibit users that have already set the IP precedence from acquiring better service for their traffic simply by setting a high precedence for all of their packets.

The class-based unconditional packet marking and LLQ features can use the IP precedence bits.

IP Precedence Compared to IP DSCP Marking

If you need to mark packets in your network and all your devices support IP DSCP marking, use the IP DSCP marking to mark your packets because the IP DSCP markings provide more unconditional packet marking options. If marking by IP DSCP is undesirable, however, or if you are unsure if the devices in your network support IP DSCP values, use the IP precedence value to mark your packets. The IP precedence value is likely to be supported by all devices in the network.

You can set up to 8 different IP precedence markings and 64 different IP DSCP markings.

Conditional Marking of MPLS Experimental bits for L3VPN Traffic

The conditional marking of MPLS experimental bits is achieved for Layer 3 Virtual Private Network (L3VPN) traffic by applying a combination of ingress and egress policy-maps on the Provider Edge (PE) router. In the ingress policy-map, the qos-group or discard-class is set either based on the result of the policing action or implicitly. The egress policy-map matches on qos-group or discard-class and sets the mpls experiment bits to the corresponding value.

This feature is supported on both IPv4 and IPv6 traffic in the L3VPN network. Conditional marking can be used to mark the MPLS experimental bits differently for in-contract and out-of-contract packets. In-contract packets are the confirmed packets with the color green and discard-class set to 0. Out-of-contract packets are the packets which have exceeded the limit and have the color yellow and discard-class set to 1.

Conditional marking of MPLS experimental bits for L3VPN traffic is supported on both physical and bundle main interfaces as well as sub-interfaces.

Restrictions for Conditional Marking of MPLS Experimental bits on L3VPN

In the case of two PE routers connected back-to-back and the only label that the traffic between the routers have is the BGP label, then the explicit null label should be configured.
A maximum of three policy-maps which perform conditional marking of MPLS experimental bits can be configured per Network Processor Unit (NPU) of the Cisco NCS 5500 Series Routers.
In the ingress policy-map if qos-group is being set for the incoming traffic packets, then setting of dscp and mpls experimental bits will not work.
Both the ingress and egress policy-maps must be applied in order to attain the expected behaviour. If either one of them is not applied then it may lead to undefined behaviour.
If the egress policy-map does not match on qos-group or discard-class and set the mpls experiment bits to the required value, then the mpls experimental bits will be set to a value of zero, by default.

QoS DSCP Preservation

Table 5. Feature History Table
Feature Name	Release Information	Feature Description
QoS DSCP Preservation	Release 7.2.1	This feature is now also supported on routers that have the Cisco NC57 line cards installed and operate in the native mode.

The DSCP value of the packet is preserved only for L3VPN networks when the packets are destined to the directly connected routes on the PE routers. To preserve the DSCP value for packets to destinations beyond the egress PE routers for L3VPN, you should use the label mode per-vrf command under the VRF at the PE routers. Similarly for MPLS networks, the default behaviour is uniform mode where the penultimate hop copies the MPLS EXP bit to IP DSCP and IP DSCP value is not preserved beyond the egress PE router. To preserve the IP DSCP value, you should use the mpls ip-ttl-propagate disable command at the penultimate hop.

DSCP value preservation is not supported on NC57-24DD and NC57-18DD-SE line cards for Cisco IOS XR Release 7.0.2.

Policy-map for conditional marking of incoming IPv4 and IPv6 traffic

The incoming packets are classified based on the ingress policy-map and the following actions are done.

Set qos-group
Discard class or drop precedence is set implicitly or as a result of a policing action.
Packets that violate the configured policer are dropped in the ingress processing itself.

Running Configuration:

policy-map ingress
 class af11
  police rate percent 10 peak-rate percent 20 
  ! 
  set qos-group 1
 ! 
 class af22
  police rate percent 30 peak-rate percent 50 
  ! 
  set qos-group 2
 ! 
 class af32
  set qos-group 3
  police rate percent 30 peak-rate percent 60 
  ! 
 ! 
 class class-default
 ! 
 end-policy-map
!

Policy-map for conditional marking of outgoing MPLS traffic

The IPv4 or IPv6 ingress packet undergoes MPLS encapsulation during the egress processing in the PE router which performs the label imposition. The MPLS experimental bits are marked on the basis of egress policy-map which performs the following actions:

Match on qos-group or discard class or both
Set the MPLS experimental bits based on the match criteria

Running Configuration:

policy-map egress
 class qos1_disc0 # This class matches on qos-group 1 and discard-class 0
  set mpls experimental imposition 1
 ! 
 class qos1_disc1 # This class matches on qos-group 1 and discard-class 1
  set mpls experimental imposition 5
 ! 
 class qos2_disc0 # This class matches on qos-group 2 and discard-class 0
  set mpls experimental imposition 2
 ! 
 class qos2_disc1 # This class matches on qos-group 2 and discard-class 1
  set mpls experimental imposition 6
 ! 
 class qos3_disc0 # This class matches on qos-group 3 and discard-class 0
  set mpls experimental imposition 3
 ! 
 class qos3_disc1 # This class matches on qos-group 3 and discard-class 1
  set mpls experimental imposition 7
 ! 
 class class-default
 ! 
 end-policy-map
!

Conditional Marking of MPLS Experimental bits for L2VPN Traffic

Note

This feature is not available on NC57-24DD and NC57-18DD-SE line cards for Cisco IOS XR Release 7.0.2.

This feature is supported on Virtual Private Wire Service (VPWS), and Virtual Private LAN Service (VPLS) traffic in the L2VPN network, and currently not supported for Ethernet Virtual Private Network (EVPN).

The conditional marking of MPLS experimental bits is achieved for Layer 2 Virtual Private Network (L2VPN) traffic by applying a combination of ingress and egress policy-maps on the Provider Edge (PE) router. In the ingress policy-map, the qos-group or discard-class is set either based on the result of the policing action or implicitly. The egress policy-map matches on qos-group or on a combination of qos-group and discard-class and sets the mpls experiment bits to the corresponding value.

Conditional marking can be used to mark the MPLS experimental bits differently for in-contract and out-of-contract packets. In-contract packets are the confirmed packets with the color green and discard-class set to 0. Out-of-contract packets are the packets which have exceeded the limit and have the color yellow and discard-class set to 1.

Conditional marking of MPLS experimental bits for L2VPN traffic is supported on both physical and bundle main interfaces as well as sub-interfaces.

Restrictions for Conditional Marking of MPLS Experimental bits on L2VPN

In the case of two PE routers connected back-to-back and the only label that the traffic between the routers have is the BGP label, then the explicit null label should be configured. 
A maximum of two policy-maps which perform conditional marking of MPLS experimental bits can be configured per Network Processor Unit (NPU) of the Cisco NCS 5500 Series Routers. However, the same policy can be applied on multiple interfaces on the same NPU.
In the ingress policy-map if qos-group is being set for the incoming traffic packets, then setting of dscp and mpls experimental bits will not work.
Both the ingress and egress policy-maps must be applied in order to attain the expected behaviour. If either one of them is not applied then it may lead to undefined behaviour.
If the egress policy-map does not match on qos-group or discard-class and set the mpls experiment bits to the required value, then the mpls experimental bits will be set to a value of zero, by default.

Policy-map for conditional marking of incoming traffic

The incoming packets on the Power Edge router are classified based on the ingress policy-map and these actions are taken.

Set qos-group
Discard class or drop precedence is set implicitly or as a result of a policing action.
Set traffic class
Packets that violate the configured policer are dropped in the ingress processing itself.

Running Configuration:

class-map af11
   match cos 1
!

policy-map ingress
 class af11
  police rate percent 10 peak-rate percent 20 
  ! 
  set qos-group 1
  set Traffic-class 3
 ! 
 class class-default
 ! 
 end-policy-map
!

Policy-map for conditional marking of outgoing MPLS traffic

The ingress packet undergoes MPLS encapsulation during the egress processing in the PE router which performs the label imposition. The MPLS experimental bits are marked on the basis of egress policy-map which performs the following actions:

Match on qos-group or discard class or both
Set the MPLS experimental bits based on the match criteria

Running Configuration:

class-map match-all qos-group2_0
   match qos-group 2
   match discard-class 0

policy-map egress-marking
 class qos-group2_0 # This class matches on qos-group 2 and discard-class 0
  set mpls experimental imposition 1
 ! 
 class class-default
 ! 
 end-policy-map
! 
policy-map Egress-Queuing
 class Traffic-class3
  shape average 500 mbps
! 
 class class-default
!
end-policy-map
!

Conditional Marking of MPLS Experimental Bits for EVPN-VPWS Single-Homing Services

Table 6. Feature History Table
Feature Name	Release Information	Feature Description
Conditional Marking of MPLS Experimental Bits for EVPN-VPWS Single-Homing Services	Release 7.3.1	This feature enables you to differentiate traffic in the MPLS forwarding domain and manage traffic from ingress PE to egress PE based on the MPLS EXP bit of the MPLS header. This feature is supported only for EVPN-VPWS single-homing services, and not supported for EVPN-VPWS multi-homing services.

The conditional marking of MPLS experimental bits is achieved for EVPN-VPWS single-homing services by applying a combination of ingress and egress policy-maps on the provider edge (PE) router. In the ingress policy-map, the qos-group or discard-class is set either based on the result of the policing action or implicitly. The egress policy-map matches on qos-group or on a combination of qos-group and discard-class and sets the MPLS experiment bits to the corresponding value.

Conditional marking can be used to mark the MPLS experimental bits differently for in-contract and out-of-contract packets. In-contract packets are the confirmed packets with the color green and discard-class set to 0. Out-of-contract packets are the packets that have exceeded the limit and have the color yellow and discard-class set to 1.

Conditional marking of MPLS experimental bits for EVPN-VPWS single-homing services are supported on both physical and bundle main interfaces as well as sub-interfaces.

Configuration

The ingress policing is applied on the UNI interface. It is with set qos-group and set traffic class.
The marking policy is applied at the core facing NNI interface.
MPLS EXP imposition is marked while packets egress from NNI Interface.

Running Configuration


interface TenGigE0/0/0/2.203 l2transport  => This is UNI
encapsulation dot1q 203
service-policy input pol50-100
 
interface TenGigE0/0/0/10  ===============> This is the core NNI
description *** CORE IF  ***
cdp
service-policy input in_mpls
service-policy output eg_mark
ipv4 address 192.18.44.18 255.255.255.0
ipv6 address 2005:18:44::18/48
lldp
  enable
!
monitor-session test ethernet direction tx-only port-level
!
load-interval 30
!
l2vpn
xconnect group 203
  p2p 203
   interface TenGigE0/0/0/2.203
   neighbor evpn evi 1 service 203
 
policy-map pol50-100
class class-default
  set traffic-class 2
  set qos-group 4
  police rate 50 mbps peak-rate 100 mbps
  !
!
end-policy-map
!
 
policy-map eg_mark
class qg4dc0
  set mpls experimental imposition 2
!
class qg4dc1
 set mpls experimental imposition 3
!
class class-default
!
end-policy-map
!
class-map match-all qg4dc0
match qos-group 4
match discard-class 0
end-class-map
!
 
class-map match-all qg4dc1
match qos-group 4
match discard-class 1
end-class-map

Verification

Verify that you have configured conditional marking of MPLS experimental bits for EVPN-VPWS single-homing services successfully.


Router#show qos int tenGigE 0/0/0/2.101 input
NOTE:- Configured values are displayed within parentheses
Interface TenGigE0/0/0/2.101 ifh 0x41da  -- input policy
NPU Id:                        0
Total number of classes:       1
Interface Bandwidth:           10000000 kbps
Policy Name:                   pol50-100
Accounting Type:               Layer1 (Include Layer 1 encapsulation and above)
------------------------------------------------------------------------------
Level1 Class                             =   class-default
New traffic class                        =   2
New qos group                            =   4
 
Policer Bucket ID                        =   0x18
Policer Stats Handle                     =   0x0
Policer committed rate                   =   49219 kbps (50 mbits/sec)
Policer peak rate                        =   98438 kbps (100 mbits/sec)
Policer conform burst                    =   62336 bytes (default)
Policer exceed burst                     =   187008 bytes (default)
-------------------------------------------------------------------------------

Router#show qos int tenGigE 0/0/0/10 output
Tue Sep  1 04:18:27.508 UTC
NOTE:- Configured values are displayed within parentheses
Interface TenGigE0/0/0/10 ifh 0xe0  -- output policy
NPU Id:                        0
Total number of classes:       3
Interface Bandwidth:           10000000 kbps
Policy Name:                   eg_mark
VOQ Base:                      0
Accounting Type:               Layer1 (Include Layer 1 encapsulation and above)
------------------------------------------------------------------------------
Level1 Class                             =   qg4dc0
New imposition exp                       =   2
Queue Max. BW.                           =   no max (default)
Queue Min. BW.                           =   0 kbps (default)
Inverse Weight / Weight                  =   0 / (BWR not configured)
 
Level1 Class                             =   qg4dc1
New imposition exp                       =   3
Queue Max. BW.                           =   no max (default)
Queue Min. BW.                           =   0 kbps (default)
Inverse Weight / Weight                  =   0 / (BWR not configured)
 
Level1 Class                             =   class-default
Queue Max. BW.                           =   no max (default)
Queue Min. BW.                           =   0 kbps (default)
Inverse Weight / Weight                  =   0 / (BWR not configured)
------------------------------------------------------------------------------

Classifying Packets Based On MPLS Experimental Bits in MPLS Over GRE

Table 7. Feature History Table
Feature Name	Release Information	Feature Description
Classifying Packets Based On MPLS Experimental Bits in MPLS Over GRE	Release 7.3.4	For MPLS over GRE scenarios that tunnel MPLS traffic over non-MPLS networks, you can now perform QoS classification for specific traffic or applications based on MPLS EXP bit field values in the MPLS header. In earlier releases, you could perform QoS classification only in the outer GRE IP header using DiffServ Code Point (DSCP) or IP precedence bits that helped you achieve the required line rate minus the granularity. This feature introduces the hw-module profile qos gre-exp-classification-enable command.

You can now perform QoS classification based on the MPLS header that the GRE IP header encapsulates in a single-pass GRE scenario. This classification takes place on the MPLS labels (specifically the experimental bits or EXP) in the MPLS header after the GRE is decapsulated using Policy-Based Routing (PBR). Because the MPLS labels identify specific customer traffic and applications, the classification is more granular. As the traffic moves along the single-pass GRE, the POP tag removes the MPLS header, and the outgoing traffic with QoS classification has the inner IP header. (Also, see Terms Used for Classifying Packets Based On MPLS Experimental Bits in MPLS Over GRE.)

To enable QoS classification on the inner MPLS header, run the command hw-module profile qos gre-exp-classification-enable .

Note

Ensure that you reload the line card for this command to take effect. If you don't reload the line card, QoS classification will continue on the outer GRE IP header with DSCP or IP precedence marking.

To understand how this functionality works, see the figure QoS Classification on Inner MPLS Header for MPLS over GRE.

Figure 3. QoS Classification on Inner MPLS Header for MPLS over GRE

The MPLS packet approaches the beginning of the GRE tunnel. The GRE tunnel is configured across a non-MPLS network on the provider edge (PE) devices, PE1 and PE2, which are at either end of the tunnel.
GRE encapsulation is added at tunnel entry point.
The MPLS packet traverses the non-MPLS network, where only the outer IP header is parsed by routers.
When the packet reaches the ingress interface (Eth 1/0) on router PE2, QoS classification is performed based on MPLS EXP bits. Before the packet reaches the egress interface (Eth 0/0) of PE2, the outer GRE header is removed.
The packet with the MPLS header now travels toward its ultimate destination to CE2.

Behavioral Specifications

This feature is supported only in scenarios where you enable GRE single-pass. (You configure the tunnel mode gre ipv4 encap command in GRE single-pass. See Set Up and Configuration for QoS Classification on MPLS Header.)
To preserve the inner DSCP markings and IP Time-to-Live (TTL) values, you must disable the propagation of IP Time-to-Live (TTL) to and from the MPLS header for forwarded and local packets. See mpls ip-ttl-propagate .

Restrictions

Set Up and Configuration for QoS Classification on MPLS Header

This section describes the configuration details for QoS classification on the MPLS header in a single pass GRE tunnel per the Figure QoS Classification on Inner MPLS Header for MPLS over GRE.

Configuration for PE1 (encap node) where you:

enable GRE single-pass.
assign the GRE tunnel source and destination addresses.
assign IPv4 addresses for PE1 and PE2.

Router(config)#interface tunnel-ip_intf1
Router(config-if)#ipv4 address 203.0.113.1 255.255.255.252
Router(config-if)#tunnel mode gre ipv4 encap
Router(config-if)#tunnel source 13.1.1.1
Router(config-if)#tunnel destination 11.1.1.1
Router(config-if)#root
Router(config)#interface Eth 1/0
Router(config-if)#ipv4 address 209.165.201.1 255.255.255.224
Router(config-if)#exit
Router(config-if)#interface Eth 0/0
Router(config-if)#ipv4 address 198.51.100.1 255.255.255.0
Router(config-if)#commit

Configuration for intermediate hop router (P1) where you configure the forwarding addresses for packets.

Router(config)#interface Eth1/0
Router(config-if)#ipv4 address 198.51.100.2 255.255.255.0
Router(config-if)#root
Router(config)#
Router(config)#interface Eth0/0
Router(config-if)#ipv4 address 203.0.113.1 255.255.255.0
Router(config-if)#root
Router(config)#commit

Configuration for intermediate hop router (P2) where you configure the forwarding addresses for packets.

Router(config)#interface Eth1/0
Router(config-if)#ipv4 address 203.0.113.2 255.255.255.0
Router(config-if)#root
Router(config)#
Router(config)#interface Eth0/0
Router(config-if)#ipv4 address 192.0.2.1 255.255.255.0
Router(config-if)#root
Router(config)#commit

Configuration for PE2 (decap node) where you:

disable TTL to preserve the IP header DSCP and TTL.

configure hw-module profile qos gre-exp-classification-enable .

Note

Ensure that you reload the line card for this command to take effect. If you don't reload the line card, QoS classification will continue on the outer GRE IP header with DSCP or IP precedence marking. We recommend that you use the hw-module location all reload command in Sysadmin VM.

configure MPLS EXP bits, class-map, and the policy-map before decapsulation.

Router(config)#mpls ip-ttl-propagate disable
Router(config)# hw-module profile qos gre-exp-classification-enable
NOTE:To activate this profile, you must manually reload the chassis/all line cards
Router(config)#
#reload the device to get effect of qos gre-exp-classification
/*We recommend that you use the hw-module location all reload  command in Sysadmin VM*/
Router#admin
root connected from 192.0.108.4 using ssh on sysadmin-vm:0_RP0
sysadmin-vm:Router#hw-module location all reload
!

/*After reloading, configure MPLS exp bits, class-map, and the policy-map*/
Router(config)#class-map match-any exp1
Router(config-cmap)#match mpls experimental topmost 1
Router(config-cmap)#end-class-map
Router(config)#class-map match-any exp2
Router(config-cmap)#match mpls experimental topmost 2
Router(config-cmap)#end-class-map
Router(config)#class-map match-any cs1
Router(config-cmap)#match dscp cs1
Router(config-cmap)#end-class-map
Router(config)#policy-map gre-ip_in
Router(config-pmap)#class exp1
Router(config-pmap-c)#set traffic-class 1
Router(config-pmap-c)#exit
Router(config-pmap)#class exp2
Router(config-pmap-c)#set traffic-class 2
Router(config-pmap-c)#exit
Router(config-pmap)#class class-default
Router(config-pmap-c)#exit
Router(config-pmap)#end-policy-map
Router(config)#
Router(config)#interface Eth0/0
Router(config-if)#service-policy input gre-ip_in
Router(config-if)#ipv4 address 192.0.2.2 255.255.255.0
Router(config-if)#load-interval 30
Router(config)#
Router(config)#interface Eth1/0
Router(config-if)#ipv4 address 209.165.202.129 255.255.255.224
Router(config-if)#load-interval 30
Router(config-if)#root
Router(config-if)#commit

Running Configuration

interface tunnel-ip_intf1 
 ipv4 address 203.0.113.1 255.255.255.252 
 tunnel mode gre ipv4 encap 
 tunnel source 13.1.1.1 
 tunnel destination 11.1.1.1 
!
interface Eth 1/0 
 ipv4 address 209.165.201.1 255.255.255.224 
 
!
 
interface Eth 0/0 
 ipv4 address 198.51.100.1 255.255.255.0
 
!
!

/*Configuration for intermediate hop router (P1)*/
interface Eth1/0 
 ipv4 address 198.51.100.2 255.255.255.0 
 
! 

interface Eth0/0 
 ipv4 address 203.0.113.1 255.255.255.0 

!
!
/*Configuration for intermediate hop router (P2)*/
interface Eth1/0 
 ipv4 address 203.0.113.2 255.255.255.0 
!
interface Eth0/0 
 ipv4 address 192.0.2.1 255.255.255.0 

!
!
mpls ip-ttl-propagate disable 
hw-module profile qos gre-exp-classification-enable 
reload loc all 
class-map match-any exp1 
 match mpls experimental topmost 1 
 end-class-map 

!
class-map match-any exp2 
 match mpls experimental topmost 2 
 end-class-map 
! 
class-map match-any cs1 
 match dscp cs1 
 end-class-map 
!
policy-map gre-ip_in 
 class exp1 
  set traffic-class 1 
 
! 
 class exp2 
  set traffic-class 2 
 
!
 class class-default 
 
!
end-policy-map 
!
interface Eth0/0 
 service-policy input gre-ip_in 
 ipv4 address 192.0.2.2 255.255.255.0 
 load-interval 30 

! 
interface Eth1/0 
 ipv4 address 209.165.202.129 255.255.255.224 
 load-interval 30 
!

Verification

Run the show policy-map command on PE2 (decapsulation node) to view the classification statistics that confirm QoS classification is on the MPLS header.

Router#show policy-map int Eth1/0
Eth1/0 input: gre-ip_in
 
Class exp1
  Classification statistics          (packets/bytes)     (rate - kbps)
    Matched             :            55436316/8426320032           504105
    Transmitted         :            55436316/8426320032           504105
    Total Dropped       :                   0/0                    0
Class exp2
  Classification statistics          (packets/bytes)     (rate - kbps)
    Matched             :            55436286/8426315472           504105
    Transmitted         :            55436286/8426315472           504105
    Total Dropped       :                   0/0                    0
Class class-default
  Classification statistics          (packets/bytes)     (rate - kbps)
    Matched             :                   0/0                    0
    Transmitted         :                   0/0                    0
    Total Dropped       :                   0/0                    0
Policy Bag Stats time: 1648011883484

When you don't enable QoS classification on the MPLS header, the show policy-map command on PE2 (decapsulation node) confirms that the classification is IP precedence (under class-default ).

Router#show policy-map int Eth1/0
Eth1/0 input: gre-ip_in
 
Class exp1
  Classification statistics          (packets/bytes)     (rate - kbps)
    Matched             :                   0/0                    0
    Transmitted         :                   0/0                    0
    Total Dropped       :                   0/0                    0
Class exp2
  Classification statistics          (packets/bytes)     (rate - kbps)
    Matched             :                   0/0                    0
    Transmitted         :                   0/0                    0
    Total Dropped       :                   0/0                    0
Class class-default
  Classification statistics          (packets/bytes)     (rate - kbps)
    Matched             :           108028694/16420361488          1008187
    Transmitted         :           108028694/16420361488          1008187
    Total Dropped       :                   0/0                    0
Policy Bag Stats time: 1648013053478

Terms Used for Classifying Packets Based On MPLS Experimental Bits in MPLS Over GRE

Generic Routing Encapsulation (GRE)

A protocol used to encapsulate packets, GRE is useful when you need to transport packets across an unsupported network protocol, say IPv6 packets across an IPv4 network. In this case, IPv6 packets are encapsulated or wrapped around by packets that support the protocol (IPv4) and transported across the network. This is akin to cars being transported across oceans (unsupported protocol for cars) on cargo ships (the ocean being the supported protocol for the ships).

GRE Tunneling

The encapsulation of packets within other packets is called GRE tunneling. Here, if packets are to be transported from one router to another without any additional processing by intermediate routers and devices, you can configure a GRE tunnel between the two routers. As the packets flow across the network, the intermediate routers read the forwarding information on the packet headers and send them to their next hop. This is similar to the cars now being transported on a cargo truck on land, passing through a tunnel to reach the other end of the road faster, with no other action taking place on the cars as they are carried on the truck inside the tunnel. Without the tunnel, transport across this route would be impossible, akin to an unsupported network between the two ends of the GRE tunnel.

GRE Headers

Each packet consists of the payload—the actual packet content—and an IP header that contains information critical for the packet transportation: the source address, the destination address, packet number, packet length, and so on.

As with other network protocols, GRE adds its own headers to the packets: the GRE header that shows the protocol used by the encapsulated packet (the cars, in our preceding example) and an outer IP header that wraps the encapsulated packet’s payload and IP header. A GRE header thus has two IP headers.

MPLS over GRE

A mechanism for tunneling MPLS packets over non-MPLS networks by creating a GRE tunnel across a non-MPLS network. The MPLS packets are encapsulated within the GRE tunnel packets, and the encapsulated packets traverse the non-MPLS network through the GRE tunnel. When GRE tunnel packets reach the other side of the non-MPLS network, the GRE tunnel packet header is removed and the inner MPLS packet is forwarded to its final destination.

QPPB

QoS Policy Propagation via BGP (QPPB) is a mechanism that allows propagation of quality of service (QoS) policy and classification by the sending party that is based on the following:

Access lists
Community lists
Autonomous system paths in the Border Gateway Protocol (BGP)

Thus, helps in classification that is based on the destination address instead of the source address.

QoS policies that differentiate between different types of traffic are defined for a single enterprise network. For instance, one enterprise may want to treat important web traffic, not-important web traffic, and all other data traffic as three different classes. And thereafter, use the different classes for the voice and video traffic.

Hence, QPPB is introduced to overcome the following problems:

The administrative challenges of classifying that is based on ACLs.
The administrative problems of just listing the networks that need premium services.

QPPB allows marking of packets that are based on QoS group value associated with a Border Gateway Protocol (BGP) route.

Benefits of QPPB

QPPB provides an IP prefix-based QoS capability.
Traffic to IP addresses that have specific IP prefixes can be prioritized above other IP addresses.
IP prefixes of interest are tagged through the control plane that uses common BGP route-map techniques, including the community attribute.
Traffic to the tagged BGP prefixes is then classified and prioritized via the data forwarding plane by using the IOS-XR MQC (Modular QoS CLI) mechanisms, such as re-marking.
QPPB provides the glue between the BGP control plane and the IP data forwarding plane in support of IP prefix-based QoS.
BGP configuration within QPPB uses a table map to match specific prefixes learned through BGP neighbors, and then sets the router’s local QoS Group variable maintained within the Forwarding Information Base (FIB) for those specific prefixes.
The router supports a subset of full QPPB options - only IP destination prefix mode on input policy is supported.

Router A learns routes from AS 200 and AS 100. QoS policy is applied to any ingress interface of Router A to match the defined route maps with destination prefixes of incoming packets. Matching packets on Router A to AS 200 or AS 100 are sent with the appropriate QoS policy from Router A.

BGP maintains a scalable database of destination prefixes, QPPB, by using BGP table maps. BGP adds the ability to map a qos-group value to desired IP destinations. These qos-group values are used in QOS policies applied locally on ingress interfaces. Whenever a packet bound for such destinations is encountered, the qos-group value matching that destination route looks up with work inside the policy classmap, and marks that packet for any configured policy actions.

QPPB: Guidelines and Limitations

QPPB is supported only on the -SE variants of NCS 5700-line card-based routers and the following -SE variants of NCS 5500-line card-based routers:
- NCS-55A1-36H-SE-S
- NCS-55A2-MOD-SE-H-S
- NCS-55A2-MOD-SE-S
- NC55-36x100G-A-SE
- NC55-MOD-A-SE-S
QPPB doesn’t work for /32 IPv4 prefixes on NCS 5500 line card-based routers when you enable the hw-module fib mpls label lsr-optimized profile.
You must configure the hw-module profile qos ipv6 short command for QPPB to work with IPv6 address families and packets.
When you enable the peering mode (using the hw-module profile qos ingress-model peering command), the QPPB feature doesn’t work.

Configuration Workflow

Use the following configuration workflow for QPPB:

Define route policy.
Put Route policy at table-policy attach point under BGP.
Define classmaps and ingress policy to use the qos-groups that are used in table-policy.
Enable ipv4/ipv6 QPPB configuration under the desired interfaces.
Configure the QPPB hardware profile, hw-module profile qos ipv6 short.
If you use ipv6 QPPB, you must reload that linecard. If you use only ipv4 QPPB, linecard reload is not mandatory.

Define route policy

A routing policy instructs the router to inspect routes, filter them, and potentially modify their attributes as they are accepted from a peer, advertised to a peer, or redistributed from one routing protocol to another.

The routing policy language (RPL) provides a language to express routing policy. You must set up destination prefixes either to match inline values or one of a set of values in a prefix set.

Example:

prefix-set prefix-list-v4
    70.1.1.1,
    70.2.1.0/24,
    70.2.2.0/24 ge 28,
    70.2.3.0/24 le 28
end-set
prefix-set prefix-list-v6
    2001:300::2,
    2003:200::3
end-set
  
route-policy qppb1
    if destination in (60.60.0.2) then
        set qos-group 5
    elseif destination in prefix-list-v4 then
        set qos-group 4
    else
        set qos-group 1
     pass 
endif
end-policy

For NC57 line cards, the set qos-group value under the route policy for QPPB support is 0-15. Even though the set qos-group value option displays supported values <0-31> as show below, the configuration fails for any value above 15 for NC57 line cards.

RP/0/RP0/CPU0:Fretta(config-rpl-if)#set qos-group ?
  <0-31>     decimal number

Put Route policy at table-policy attach point under BGP

The table-policy attach point permits the route policy to perform actions on each route as they are installed into the RIB routing table. QPPB uses this attachment point to intercept all routes as they are received from peers. Ultimately the RIB will update the FIB in the hardware forwarding plane to store destination prefix routing entries, and in cases where table policy matches a destination prefix, the qos-group value is also stored with the destination prefix entry for use in the forwarding plane.

Example:

router bgp 900
    [vrf <name>]
    bgp router-id 22.22.22.22
    address-family ipv4 unicast
        table-policy qppb1
    address-family ipv6 unicast
        table-policy qppb2
    neighbor 30.2.2.1 
        remote-as 500
        address-family ipv4 unicast   
            route-policy pass in
            route-policy pass out	
        address-family ipv6 unicast
            route-policy pass in
            route-policy pass out

Ingress interface QOS and ipv4/ipv6 bgp configuration

QPPB would be enabled per interface and individually for V4 and V6. An ingress policy would match on the qos groups marked by QPPB and take desired action.

If a packet is destined for a destination prefix on which BGP route policy has stored a qos-group, but it ingresses on an interface on which qppb is not enabled, it would not be remarked with qos-group.

Earlier, router supported matching on qos-group only in peering profile ‘hw-module profile qos ingress-model peering location <>’ . QPPB now permits classmaps to match qos-group in the default “non peering mode qos” as well. Also QPPB and hierarchical QOS policy profiles can work together if Hqos is used.

Example:

class-map match-any qos-group5
    match qos-group 5
    end-class-map
 
class-map match-any qos-group4
    match qos-group 4  
    end-class-map
  
policy-map ingress-marker-po1
    class qos-group5
        set precedence 0
        set discard-class 0 
        set traffic-class 1 
   
    class qos-group4
        set precedence 1
        set discard-class 1
        set traffic-class 2
    class class-default
   
end-policy-map

Configuring QPPB on an Interface

RP/0/RP0/CPU0:router # configure

Enters interface configuration mode and associates one or more interfaces to the VRF.
```
RP/0/RP0/CPU0:router(config)# interface 
type interface-path-id 
```
Enters interface configuration mode and associates one or more interfaces to the VRF.
ipv4 | ipv6 bgp policy propagation inputqos-groupdestination
Example:
```
RP/0/RP0/CPU0:router(config-if)# ipv4 bgp policy propagation input qos-group destination
```
Enables QPPB on an interface
commit

Egress Interface Configuration

The traffic-class set on ingress has no existence outside the device. Also, traffic-class is not a part of any packet header but is associated internal context data on relevant packets. It can be used as a match criteria in an egress policy to set up various fields on the outgoing packet or shape flows.

Restrictions:

No IP precedence marking.
No policing on egress policy.

class-map match-any level1
     match traffic-class 1
end-class-map

class-map match-any level2
    match traffic-class 2
end-class-map

policy-map output-po1
    class level1
        bandwidth percent 50
    class level2
        bandwidth percent 20
        queue-limit 50 ms
end-policy-map

interface hun 0/5/0/0
     ipv4 address 30.1.1.1/24
     ipv6 address 2001:da8:b0a:12f0::1/64
     service-policy output output-po1

Bias-Free Language

Results

Chapter: Configuring Modular QoS Service Packet Classification

Configuring Modular QoS Service Packet Classification

Packet Classification Overview

Traffic Class Elements

Default Traffic Class

Create a Traffic Class

Configuration Example

Related Topics

Associated Commands

Traffic Policy Elements

Create a Traffic Policy

Configuration Example

Related Topics

Associated Commands

Scaling of Unique Ingress Policy Maps

Limitations and Restrictions

Attach a Traffic Policy to an Interface

Configuration Example

Running Configuration

Verification

Related Topics

Associated Commands

Packet Marking

Packet Marking Guidelines and Limitations

Supported Packet Marking Operations

Class-based Unconditional Packet Marking

QoS Re-marking of IP Packets in Egress Direction

Configuration Example

Running Configuration

QoS Re-marking of Ethernet Packets in Egress Direction

QoS L2 Re-marking of Ethernet Packets in Egress Direction

Running Configuration

QoS L2 Re-Marking of Ethernet Packets on L3 Flows in Egress Direction

Restrictions

Running Configuration

QoS L2 Re-Marking of Ethernet Packets on L3 Flows in Egress Direction on L3 sub-interfaces

Restrictions

Running Configuration

Bundle Traffic Policies

Shared Policy Instance

Restrictions and Guidelines

Attaching a Shared Policy Instance to Multiple Subinterfaces

Running Configuration

Verification

Ingress Short-Pipe

Restrictions and Other Important Points

Configure Ingress Short-Pipe

Associated Commands

Selective Egress Policy-Based Queue Mapping

Restrictions and Other Important Points

Configure Selective Egress Policy-Based Queue Mapping

Verification

Use Case

Configuring QoS Groups with an ACL

Supported ACL Types

Prerequisites

Configuration

Running Configuration

Configuring an ACL with Fragment Match

Restrictions and Guidelines

Configuring an ACL with Fragment Match

For IPv4 and IPv6 ACLs

Running Configuration

Verification

Restrictions

Restrictions for Peering QoS Profile

Restrictions for QoS on BVI

Restrictions for Egress Drop Action

In-Place Policy Modification

Verification

Specification of the CoS for a Packet with IP Precedence

IP Precedence Bits Used to Classify Packets

IP Precedence Value Settings

IP Precedence Compared to IP DSCP Marking

Conditional Marking of MPLS Experimental bits for L3VPN Traffic

Restrictions for Conditional Marking of MPLS Experimental bits on L3VPN

QoS DSCP Preservation